I have seen this kinda pad for the Motorola Milestone/Droid that seems pretty cool:



http://sites.google.com/site/gamegripper/home

I don't know if it would be comfortable enough but at least you can avoid extra CPU/battery usage of other bluetooth devices.

It's possible to request availability for the N900 on this page:
http://sites.google.com/site/gamegri...s/request-form

I have asked for a black one with red buttons and a six-buttons layout (for CPS2 games).