Android + Googles openscr app making API that is free and you can make money of apps you make in C or Java that run on android and that's the start of it if you root it you can do much more.
And this is it you can use java also http://developer.android.com/sdk/index.html
But to make it so others can use the apps you need to pay $25 to publish them to google play store.
And this is it you can use java also http://developer.android.com/sdk/index.html
But to make it so others can use the apps you need to pay $25 to publish them to google play store.