I have one of these in my Car:
http://www.amazon.ca/GOgroove-Transm...bUvbUpU9779123
It works awesome. I used to use it as an FM transmitter, but then I switched to using the AUX input on my Radio. But connect to it using Bluetooth on my Phone.
Only down side to an FM transmitter is if someone parks beside you on the same Radio Frequency, then they'll hear your music/phone call. hence the reason why I switched to the AUX in. the X2 has an AUX out, so I plug that into my Radio Aux IN.
Cheers