BlueAnt S4 Bluetooth Car Speakerphone Kit [USEN-BAW-S4]
My 2006 Jaguar VandenPlas had a very bad reaction with almost all bluetooth phones--they would literally kill the radio system.  I understand that this is typical of jags, volvos, and land rovers. I finally gave up and bought the Blueant S4.  This device is awesome.  It is easy to use and gives plenty of volume.  I do a lot of driving and use it constantly -- 8 months and not a single problem.  I would buy one again.