They had some info about it on Joystiq:

 

http://www.joystiq.com/2010/08/18/preview-xbox-live-on-windows-phone-7-and-launch-games/

 

They described it as:

 

"ilomilo
This is a puzzle-platformer with a co-op spin. You control two different characters (one red, one blue), switching between each to solve puzzles with the ultimate goal being to unite the two. Using an on-screen d-pad to move around, the combination of art style and extremely easy-to-get-into gameplay made this a favorite for me. Plus there are even some cool three-dimensional puzzles where you move around the world a la Super Mario Galaxy. Very neat!"