Has anyone tried a cell phone kit that uses a FM signal to get sound out of the car speakers?

I know that some cell phones cause interference with the radio. So do you think that this will have the same problem?

Specifically this one
[img] http://store6.yimg.com/I/cell-accessories_1630_1201887[/img]

more info at
http://www.cellphones-accessories.com/nok8282fmdua.html

 

I have used the Navigator kit with FM mod. The sound is decent, but the microphone is terrible. Also, most of those are not full duplex. The other person can't hear you talking until they are done - kind of like a walkie talkie. I broke down and bought the hardwire handsfree kit for my phone...