We started out writing apps for Window Mobile, a simple Stop Watch to learn the platform
Then an app to backup and clean old SMS Messages as this caused major slow downs on Windows Mobile. Then to learn the Android platform the app was ported to Android to allow the same features on Android and share your SMS message between Windows Mobile and Android
Then to get started with the new Windows Phone platform we ported the Stop Watch app
After having used Remote Desktop extensively on Windows Mobile, loving and hating it at the same time this was missing on Windows Phone. So a massive project started to make a Remote Desktop app for Windows Phone, our app was the first on Windows Phone. When Windows Phone launched it had no sockets support so to allow the app to communicate it used a pinvoke hack to import native sockets which was blocked by Microsoft Marketplace. The only other option at the time was to write a HTTP tunnelling proxy to allow access to the internet, it was very slow and only allowed access to public Remote Desktop servers. Windows Phone 7.5 added Socket support and this is now the basis for the app.
TVGuide+ and MusicPrime apps have both grown to bring some desirable features from other mobile platforms to Windows Phone. Hopefully this can continue with other apps.