Maybe something like the Ericsson Chatboard:
http://cgi.ebay.com/OEM-SONY-ERICCSON-C ... dZViewItem
There is some information available for using this keyboard through serial access to the chatboard:
http://www.brolinembedded.se/projects/keyboard (halfway down the page).
Good luck and keep us updated please!
Edit: Just realized that the article talks about the CHA-
01 and the ebay link is for a CHA-
10, so I think some Googling for valuable info about the CHA-10 would be necessary
Edit2: halfway the page in this link you see the pinout config for the CHA-10 (drawn in ascii).
http://mageforge.com/forum/viewtopic.ph ... b10aa07646