I'm pretty new at this android thing, and I'm an absolute virgin on the whole "reading several hundred posts" thing. Odds are I'll bring up an idea that's already in the store or in this thread.
Thermometer- I highly doubt this is possible but it would be interesting to have a thermometer app to go with the 9,000 weather apps. After all, the freaking thing already took my pulse. I'm sure it can handle room temperature at some point.
Google Fantasy Play- Forget that stupid Yahoo app and design the mobilest friendliest fantasy football app for android users only. Nobody would have an excuse to miss the draft. Two separate text notifications should be assigned; one to notify for every 10 points you score, another to notify for every 10 points they score. Shoot, partner up with NFL.com for their swift drafting interface.
Baseball America, Baseball Prospectus or Fangraphs- I've been using Dolphin for these all the time as mobile versions. The app could come with a drop down menu to bring up the last news for players of your choosing. Maybe they'll work together for a change and I will cut hair!