I want to create and launch an Android app. Where do I start?

Some background: I'm a web hosting professional, not a developer. I've also got a fair bit of creativity that's usually expressed in my writing, but also in building electronics and other hobbies. The largest programs I've written were 250-300 line bash scripts.

This is going to sound very cliché unfortunately, but I am serious and don't expect that anything will come easy. I have a concept for a mobile app that will interface with fitness trackers (or the phones built in gyro) in order to see if the user is active or inactive, and then it'll send them various messages about their activity.

My goal is to start by supporting Android and Fitbit and see how it goes from there. I am working toward creating my first Android app via Android Studio, but beyond that: Where do I go? What knowledge will I need to finish this and launch an app?

I appreciate any input. I know this isn't a typical HN question but I can't think of a better place to pose this question, since there are so many seasoned developers and founders here.