If you mean the Bluetooth Handsfree kits from Nokia or Sony Ericsson, then I've done the Sony HCB30 on a BMW. Worked well answering calls, providing you spend time optimising position of the mic. BUT to dial out you need to use Voice dial which was less reliable. (you can also use the phone, but that's not handsfree). Using 3+ syllable names helps. The speaker comes with the kit, and if you use this the installation is real easy, +,- and switched +.