Aren't there apps that do that? I haven't worn my Nike Fuelband for over a year but the app had social and individual challenges. IIRC the Fuelband app works w/ the AW now along with many other fitness apps.
Personally, I'd rather Apple let 3rd party devs do all this so Apple can focus on hardware and their OS. I'd be much more impressed with an AW 2 with a blood oxygen sensor or more precise HRM that really set AW apart from other smartwatches and give devs lots of possibilities.