There is in fact a company who provides Hebrew support for American Blackberries.
It enables reading and writing in Hebrew (with the help of a convenient virtual keyboard).
Does not support vowels (texts with vowels, such as Mechon Mamre's Tanakh, get a lot of black boxes in them instead).
I've been using them for a while, but lately decided it is not worth the expensive monthly subscription. METAmessage for Wireless - BlackBerry Software, Spell Check Email, Print Attachments, Print Messages, Listen Voicemail Attachments