If you live in California, you should start looking for a hands-free solution (because soon, it will the only legal way to be on a phone the the car) and the Sony Ericsson HCB-105 looks like a hassle-free one. Thanks to its clip, there’s no installation and the device is controlled with (only) two buttons. The downside is that you’ll have to charge it from time to time, although talk time is rated (by the manufacturer) at 25 hours and stand by time can be as long as 700 hours. I don’t know how good it is, but it is surely worth looking at. If you really want something slick, check Microsoft’s Sync.