Rear View Mirror with Caller ID
It always annoys me when I see people driving around holding a mobile to their ear. Hands free kits are generally pretty cheap, this one may be a bit on the expensive side but it compensates by the cool factor.
The Bluetooth Mirror is clips over your cars normal rear view mirror, it incorporates a microphone and speakers so that you can chat totally hands free and as it uses bluetooth there are no unsightly wires and you can leave your mobile in your pocket. The feature that I think is really cool is the Caller ID display, so before answering the call you can see who is calling by the number being displayed on the mirror.
The Bluetooth mirror is available from Gadget Box for £99.99.