Fujitsu and NTT DoCoMo are showing off this prototype keitai handset at the CEATEC 2008 trade show. The "Separeeto Keitai" looks like a normal keitai flip phone, but give the keypad a tug and it sunders cleanly from its magnetic hinge. Then sensors determine the keypad's orientation and contextually change the input interface, making it possible to make a phone call with the top while writing emails with the other half.
Of course you could also do this simply by wearing a Bluetooth headset, but where's the fun in that?
[CEATEC] DoCoMo's Handset Breaks Into 2 Parts, Used Separately [Video] [NikkeiBP.co.jp via CrunchGear]