I have a Logitech Dinovo Mini, it is a really good bluetooth keyboard in my opinion. I purchased it because it was easy to connect to my pc and my ps3, and hopefully maybe one day it will connect to my n900.

http://www.logitech.com/index.cfm/ke.../3848&cl=us,en

its a bit pricey, but sometimes you can get it for a good deal on sale.