Visually, I like Stockfish chess. So many of the chess apps are very cluttered and distracting--faux wood grain, 3D pieces, etc. However, Stockfish has no built-in online multiplayer feature. You'd have to email the positions back and forth. This can be done from within the program. It is nice and clean.
Doesn't Zynga, the company responsible for Words With Friends, make a Chess With Friends?
Edit: Chess With Friends is currently iPhone only--it has to be up-scaled.
Good luck. I'm interested to see what you come up with.