After creating my NodeJS module node-sgp4 and using it for a web app I created over at I wanted a way for mobile users to easily and elegantly have access to the same information. My first step was to choose what platform I would like to develop my mobile app on. While many people use iOS, Apple requires developers to pay a yearly fee of $99 which I did not want to spend on a "just for fun" app. The Android developer license is much cheaper (I believe it's somewhere around $20) and I had already paid for it a few years back. I fired up Android Studio and began to work on the app for a few hours a day over my spring break. It took a bit to get the hang of Android Studio having moved from Eclipse but I soon learned to love it. I was able to grab a Java WebSocket library to interface with my satellite data server and porting the code from the website to the app was very simple. On thing that made porting much easier was that the Google Maps Android API was pretty much identical to their JavaScript API used for websites. A problem I ran into was that Android comes in many flavors. What I mean by this is that the app would work on the PC debugger/emulator but would crash when ran on some real devices. I was able to fix this small bug (simple if statement to see if the app was run on an emulator or not) but worried my app wasn't going to work on multiple other devices. With a bit of google-fu I came across AppThwack. This is probably one of the coolest services I've seen offered. They have a bunch of physical android devices and will test your app on whichever ones you want (you even get screenshots, logs, etc...). When you sign up they give you 100 minutes of testing time and that was much more than I needed. Back on topic though, once I had finished implementing all the features into the app the last step I had was to monetize it in some way. I didn't want people to have to pay for the app, so advertisements was a good way to go. AdMob makes it simple to integrate ads and you get nice compensation for them. If people didn't want to see the ads, I also added an in-app purchase of $2 to remove all the ads. My next plans for the app include adding more satellites (there's already 5,000+), graphical settings (changing colors, thicknesses of lines, etc...), and a few more features I don't want to say anything about yet. If you'd like to download the app, you can visit Track Sats at the Google Play Store..