What's the best in-car Bluetooth device on the market?

I've got a 4500 RDS EON stereo in my Ford Fiesta Mk6 and I'm looking to try and find a Bluetooth device I can connect to this without having to buy a new car stereo. Is there anything on the market?

Can I connect my iPhone to the Bluetooth in my 2007 car?

I have just bought a 2007 Mercedes-Benz CLK. Do you know if its possible to connect my iPhone through the Bluetooth ?