How a New Father Built an iOS App For Other New Parents

Hello! What's your background, and what are you working on?

My name is Min Kwon. I'm a software engineer, and I've have been developing mobile apps since 2008. By day I work for a mobile security startup in the Washington DC metropolitan region managing a team of engineers. By night I develop apps on the side for fun.

I've had some success in the past with a game called Save Them All, which reached the top charts (#70s in games, #120s overall) back in 2012. Unfortunately, the team imploded, so it's no longer on the app store. But I'm planning on re-releasing it.

I recently launched Baby Growth Chart Percentile for iOS. It helps parents keep track of their child's growth (things like height, weight, head circumference, and BMI) by automatically calculating the percentiles and charting them on the official growth charts from the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC).

At the time of this writing, I'm projecting around $200/month. I was able to get the app to #26 in the charts in the medical category (for a brief moment!) yesterday, so I'm hoping this will translate into a larger figure next month.

What motivated you to get started with Baby Growth Chart Percentile?

I'm a parent of two young children. When you're a new parent, one of the first things the doctor will do is to scare you with those percentiles. And when doctors tell you that your brand new child is below average, you start freaking out! Who wants to hear that their baby is "below average" when she's not even a day old yet!

I looked around and tried most of the existing apps on the market to track my child's growth percentiles, but none of them met my needs. I found the percentiles inaccurate, the UIs difficult to navigate, and/or they lacked the features I wanted. So I just decided to roll out my own.

Fortuitously, I helped out a Harvard professor on a project analyzing breast milk (for toxins, macro- and micronutrients) a couple years ago. As part of that project, I also looked into the WHO growth standards, so I was already somewhat familiar with the math.

For Baby Growth Chart Percentile though, I decided to include standards from both the WHO, CDC, and Fenton (for premature babies), because the doctors recommend that you use the WHO standard for kids under two and the CDC standard for children two and older. And because the app already gets the child's growth data, I also threw in a height calculator that uses something called the Khamis-Roche method to predict height, which I hear is around 90% accurate in predicting a child's final adult height.

That wasn't my only motivation though. My first child entered kindergarten this year, and my wife decided to quit her job to focus more on his schooling by volunteering, joining the PTA, etc. The cost of living is fairly high here, so the drop from double income to single income hurt! I actually stopped buying organic fruit — no joke! :)

And here is something else I noticed. Friends and acquaintances were complaining about not getting a raise at work. People stress over getting that extra $5,000 raise, which after taxes isn't even that much. Instead of stressing over getting a raise, I decided to try something on the side to supplement my income and start building equity in myself.

What went into building the initial product?

I developed Baby Growth Chart Percentile over the course of three months. I didn't have a lot of time with a full-time job and two active kids. I'm also dealing with a couple major health issues, so that slowed me down further.

Fortunately, I already had most of the math worked out. As soon as I got it all worked out, the next challenge was charting these data points on the official graph and making sure that they were being graphed accurately.

Those three months weren't all development though. I spent some of the time A/B testing various things such as the icons, localization (very annoying), creating a blog, and studying about marketing (fun!).

I originally had a much bigger vision for the app. I wanted to track everything baby-related, such as diaper changes, feeding times, vaccinations, and more. But I finally decided to focus solely on the growth charts. I think it was the right decision, because I could have easily spent another three months on this, and half a year would have been way too long for me. That said, I do have users asking for these extra features.

The app is made natively in Objective-C together with Swift. (I used this opportunity to finally teach myself Swift — I hate those optionals!)

How have you attracted users and grown Baby Growth Chart Percentile?

I got some traction on Product Hunt, but it didn't really translate into too many downloads. I was averaging around 20-50 downloads a day. Some things I tried and learned:

• China is outpacing US downloads by a factor of greater than two.
• Outside of China and the US, people aren't spending money on the upgrades.
• Tried LinkedIn Advertising with their $50 free credit.
• Tried Facebook ads to A/B test the icon, directing users to our landing page so we could collect emails.
• Tried Facebook ads to drive app installs.
• Tried Google Adwords to drive traffic to the landing page.
• Tested Apple Search ads with their $100 free credit.
• What finally worked and propelled the app to #26 in the charts was being featured on AppAdvice on the Apps Gone Free page.

The biggest lesson I learned was about the importance of China for downloads. So make sure to localize for China.

In terms of paid ads, the return on investment was not worth it. Here are some of my thoughts on ads:

• Apple Search ads did increase downloads, but the ROI wasn't enough to justify continuously pouring money into it, so I stopped. A tip about Search ads — make sure to apply their promotional $100 credit as soon as possible, because they won't retroactively credit you. I got bit with this one.
• LinkedIn ads sounded like a good idea, targeting pediatricians, but wow are they expensive! In two days, I've already spent most of that money. The average CPC is over $7.00.
• Spent a total of $40 on Facebook ads and only collected around 20 emails. Though it was better than Google Adwords in terms of bang for the buck.
• The ability to target very specific demographics with Facebook ads is really great. But our Facebook app installation campaign was worthless. Money wasted.

Finally, about this whole B2C thing. The consumers…

I'm sure you've heard it before. It's really difficult to convert consumers into paid customers. I've tried various price points from $4.99 all way down to $0.99, but there wasn't much of a difference.

And consumers can be brutal, especially with a free app. During the paid-to-free promotion, some user left a negative review because he could not download the in-app purchase. He thought I'd purposely broken it to trick people into downloading the app.

Another user left a random negative review saying, "It looks ok. But I didn't test it." Everyone knows how important positive reviews are, and these vacuous negative reviews really bring down the average.

I poured three months of all my free time into this app, and reading feedback from some users who complain about having to pay for the upgraded version of the app because they say they can get the charts free from the doctor's office was exasperating. I'm thinking about what I can build next to target businesses instead.

What's your business model, and how have you grown your revenue?

I have a free version of Baby Growth Chart Percentile with an in-app purchase that unlocks all the features, as well as a premium version with the in-app purchase already unlocked.

The free version initially included ads. I've tried banner ads, native ads, and also interstitial ads. I've tried mediating with Mopub (AdMob, Facebook, Mobpub's marketplace). I've also tried Appodeal. For what it's worth, the one that brought the most revenue was Appodeal.

I eventually removed all the ads because it looked like I was going to bring in less than $2 per month. Some users were also complaining about the ads, which was another reason to remove them.

For my app, the engagement and session duration isn't very high. Parents simply enter the data, check the percentiles, maybe print out the official charts, then don't come back to it until their child's next doctor visit. So I believe it was ill suited for ads.

I removed the ads from the free version and simply limited the allowable growth entries to the first year of a child's life. Certain features are also locked out, such as the adult height calculator, BMI percentile, and tracking multiple children.

Most of the sales are coming from the in-app purchase. The premium verison sells around 1-2 copies per day.

What are your goals for the future?

My immediate homework is racking my brain over how to increase the conversion rate. I've also received some user feedback, so I'll be continuing to make the app better to deliver more value. Hopefully this will translate into more sales.

I released Baby Growth Chart Percentile alone, but I've actually been collaborating with a group of around 10 developers in the past 10 years or so on various side projects, such as this one called GogoPlay that makes it easy for parents to sell and trade used children's items. We recently got together again and have been talking about tackling some projects together. Right now, the problem we have is that we have way too many ideas. So we are working on focusing in on one, validating it, and then tackling it.

And I still haven't given up on games. I am going to re-release the game that's been collecting dust in my git repository, and I also have plans on releasing other games, too. In terms of getting ad revenue, I think games are where it's at.

Finally, I'm a ranked Amazon reviewer (last I checked around top 2,500), and I am thinking of some way I can leverage this to bring in some more side income. Though I don't know what or how yet. (I'd love to hear some ideas if anyone has any!)

The biggest roadblock to all this is time.

What are the biggest challenges you've faced and obstacles you've overcome?

The Baby Growth Chart Percentile project actually started as a three-member team. I was on iOS, another on Android, and someone to handle the marketing. Right now, only the iOS version is released. And I have handled all the marketing. We had some "drama yo mama" moments that I think could have been handled differently. But hindsight being 20/20… it is what it is.

One of the features I really wanted in the app was cloud sync. Naturally, I chose iCloud. I saw that other apps did not have iCloud sync, so I spent good amount of time and effort implementing the feature.

Of course, it was on release day that I happened across a page on Apple's site saying that iCloud cannot be used to store health data. So all that effort went down the drain. If you are in the health space, pay attention to HIPAA.

Have you found anything particularly helpful or advantageous?

I'm going against what I said above, but having a partner has been very helpful. Although we are no longer collaborating, during the time we were collaborating together, I leaned and relied on him for support. I still consider him a good friend, and I hope our personal relationship will withstand this little bump. I hope he releases the Android version of Baby Growth Chart Percentile soon, because he worked hard on it.

I also find reading other interviews here on Indie Hackers and elsewhere very motivating and sometimes therapeutic. You realize that you're not alone, and that others are struggling too. Misery loves company! :)

And wow, some indies have really been successful. It gives me hope that one day I can join their ranks. At this point, my goal isn't complete financial independence from my day job — just simply less dependence on it.

I also recommend checking out Rob Walling's book Start Small, Stay Small.. It's dated, but it's still very relevant and very helpful.

What's your advice for indie hackers who are just starting out?

I needed a paradigm shift in my thinking. I needed to get out of my engineer mentality. I realized that if I wanted to have any kind of success, I needed to become a marketer who was great at tech and not a techie who dabbled in marketing.

It sounds so obvious, but I didn't GET IT until recently. There was this invisible barrier in front of me blocking me from crossing that chasm, holding me back from the marketing aspect of the game.

I know plenty of developers with whom I can collaborate. But finding a great marketing person (and a graphics person) has been the most difficult thing. I finally realized that if I wanted it, I myself needed to become the expert in selling. There's still a long road ahead, and I've got a lot more to learn, but I'm glad I finally realized this.

I can't remember where I heard this, so I don't know to whom to attribute it, but it stuck with me:

"Developers who understand marketing are unstoppable."

Where can we go to learn more?

• iOS App: itunes.apple.com/us/app/baby-growth-chart-tracker/id1278595136?mt=8
• Landing page: www.growthchart.us
• Blog: www.growthchart.us/blog
• My LinkedIn: www.linkedin.com/in/minkwon/

Please feel free to reach out to me via LinkedIn or the blog's Contact Us page!