The german T-Mobile is launching Danger Inc. HipTop device under the name Sidekick in the US next week. As reported on I4U back in december 2001, Danger Inc. developed a interesting platform for data services like email and web.
Its also a phone of course.
The Sidekick features a black-and-white screen, thats maybe one if its challenges competing with for instance the color Sprint Vision phones (Samsung A500, Samsung N400, Sanyo 5300, etc.)
I saw on CNET TV that Danger will release a color version early next year.

More info on the following sites:

Danger Inc. Products

T-Mobile Sidekick

Udate 11/15/03:
Color Sidekick on Sale!