Perhaps it's a poor choice, we'll find out I suppose. The reason is mainly that I know it well, and already have an app that is featured by Apple with great ratings already. To be fair I "picked" the category 4 years ago, and I've made a lot of money in it so far. As for the current choice I suppose I could start something new from scratch, but I felt like it made more sense to pick a current app that I think has the most potential.

Runkeeper, and most of the other competitors (outside nike) make their money on IAP's for advanced features. I don't actually consider fitbit a competitor per se, it's a slightly different beast.