I don't know if Blackberry Thumb is an official medical condition, but anyone who regularly does a lot of texting or emailing on a cell phone knows what it is. According to textually.org, in New Zealand, a woman was diagnosed with "texting tenosynovitis" - an inflammation of the tendons in the thumb from excessive text messaging.
Some hotels offer Blackberry Balm massages to businessmen suffering from this ailment, but short of checking yourself into a hotel or spa, there seems to be little help for those of us addicted to texting. A couple of years ago, I did see, at a Sharper Image store, a little electronic massage machine designed for hands and wrists (similar in appearance to some neck massagers), but I haven't been able to find it again -- anywhere. If you've seen this somewhere, please let me know.
IMAK, which makes SmartGlove wrist supports for carpal tunnel (designed by an orthopedic surgeon), also makes the glove with thumb support, the idea behind it being that it holds your wrist and thumb in a position that prevents further damage. Built into the glove are something called "ergoBeads" which cushion the underside of the wrist. While I don't know what it does to reverse damage already done, it's worth a try if it can prevent more serious problems.
For myself, I'm renaming this condition "iPhone Thumb" - I still haven't gotten the hang of using that on-screen keypad, and have to type every other word twice to get it right.
Fit fingers GripGlider