Apparently T-Mobile's Sidekick mobile communicator is proving to be very popular with the deaf:
Danger was getting a lot of feedback from unexpected quarters. “We got some e-mails initially from people who were influential in the deaf community talking about how much they liked the device, and they're a great forum for providing constructive feedback,” Nothhaft said. While many deaf customers loved the SideKick, they had some suggestions: More battery life would be great. A data-minutes-only plan from wireless carrier T-Mobile would also be nice, since hearing impaired users often don't need voice minutes. And hearing-impaired gadget-lovers on online message boards — where the T-Mobile SideKick is achieving celebrity status — wanted a way to translate their text messages into voice calls.
this is an interesting 'accident of design'