UK Stops is my second published Android app, and the first one to actually make me some money! It’s in its second major version (version 2 was a complete rewrite from version 1). It’s a bit outdated now, but I’m not sure if I want to put more time into a third version. It’s fairly popular with over 20,000 downloads and 6,000 active users.
Basically it’s just a map of the UK showing bus stops and train stations. Touching any stop will pop up live departure times. You can save stops into a favourites list for easier lookup later.
The server was written in Python and hosted on Google App Engine – which is an excellent cloud platform for hosting simple services. This app engine service serves about 8 Gb of map tiles very efficiently at very low cost. So I think App Engine is really not bad.