The Panoramic Software Team has been working on a game for Windows Mobile devices called Hexegems.
Its been put together as a technology demo and I have no word yet if its going to be available to the public (either as a retail game or a free download) but I'll post again as soon as I have more information.
What I can tell you is: its great fun on my G900.
For now - here's a little eye candy.
Panoramic Software: http://www.panoramicsoft.com/