The new T-Mobile Sidekick II is now available from T-Mobile USA online store for $249.99, after a $50 "Web-only rebate".

Specifications:

Size: 5.1 x 2.6 x 0.9 inches
Weight: 7.0 oz.
Included battery: Lithium polymer
Talk time: up to 4.5 hours
Standby time: up to 2.5 days
International phone: Tri-band (1900, 1800, 900 MHz)

6 MB e-mail account included
Instant messaging 
Real web browsing
World Phone (Tri-band)
Integrated camera with flash
Speakerphone
Photo Caller ID
Vcard support
Organizer: Synchronize it all wirelessly to your desktop interface
Use text messaging to send and receive quick messages
There is a Sidekick dataplan you can subscribe with

The T-Mobile Sidekick Data Plan is for customers who just want to use the Sidekick's powerful data functionality, including unlimited e-mail, AIM, Web browsing, and text messaging for $29.99 a month, with voice calls billed on a pay-as-you-go basis for 20cents per minute, domestic long distance and roaming included.