Hi!
I just finished version 1.0 of my Windows phone 7 application.
It's called City Walk and devides a city into 50x50 meter squares. The users goal is to visit as meny of the squares as possible. Ranking lists keep track of how well you do compared to other users. Feel free to try out the fully working trial version (14 days) and give any kind of feedback.
More info at
www.powerapp.org
Regards Andreas