Handheld hardware ideas needed

I have kind of a odd question and I am really just looking for ideas. I would like to develop a platform that several people in the same room could compete aginst each other. Kind of like the trivia games you see in bars sometimes where everyone gets a wireless keyboard and there are questions up on the TVs and you answer them as they come up. Well here is my question if I were to set something like this up what would I use for the wireless keyboard. I would like them to be pretty cheap. The idea I have would involve mostly server side processing so the memory and processing power of the handheld unit would be small. It really just need to send small bits of info back to the server via local area network where it could be processed. Does anyone have any ideas of a piece of hardware that would fit these requirements? I have looked at ones like a Blackberry RIM 850 and that sort of thing?

Thanks.