Cute! The CPKB-BT make by I-O Data is a keyboard equipped with Bluetooth 2.0 and is targeted at hardcore-users of mobile blogs and email.
The wireless keyboard is just 151.5×92.1×14mm and weighs only 170g. It is powered by a pair of AA batteries, lasting a total of 2-3 months if the keyboard is used for 1 hour a day.
It is going to be available in Japan next June 11th and it is priced at 98€, not cheap enough.