You already know that it's illegal in some states to drive while talking into your handset. Even if that isn't against the law in your part of the country, going hands-free with your phone while you're behind the wheel is a smart move.

One way to do it is to wear a Bluetooth headset-you can opt for either a monaural (or mono) headset or stereo headphones. This type of in-ear setup can work great, as long as you have a secure and comfortable fit and you're able to tap buttons on the earpiece to handle calls without getting distracted.

An even better idea, however, is to use a Bluetooth speakerphone designed for your car. Consumer-ready speakerphones typically attach to your sun visor, but you'll also find units that grip your windshield or sit on your dashboard. More-sophisticated Bluetooth speakerphone car kits can also be wired into your car-usually by a mechanic, or factory-installed. For wired setups, the components are integrated with the dashboard, and some kits position the microphone on your rear-view mirror and a control widget on the steering wheel, for example. Our reviews here cover the plug-and-play kind.

Once paired with your Bluetooth cell phone, an in-car speakerphone lets you push a button to make calls and accept or reject calls. In addition, provided that your cell phone supports voice dialing, you can utter voice commands ("Call Harry Work, " for instance). Ideally you won't have to take your eyes off the road; you should be able to access the controls by feel alone. Some units also provide extra features, such as music streaming via Bluetooth and the ability to transmit sound over FM frequencies. (Theoretically, seeing as you can remove the units from your car, you could prop them up and use them as speakerphones at work or at home, too.)

In our tests, we drove many miles around city streets and on highways. While most of the Bluetooth speakerphones we tried were a breeze to install and their controls easy to locate, we were only moderately impressed with the audio quality. Don't set your expectations for call quality too high-not right now, at least. The people you talk to will probably know that you are on a speakerphone; during our tests, the quality never came close to handset-grade. Most of your conversation might be clear, but your voice could sound faint and your callers may have to endure interference, choppiness, echoes, or the like.

The $70 Motorola T305 earns the top spot on our chart of Bluetooth car kits because it's compact and ultraportable, and in tests it remained securely affixed to the visor. Additionally, the call quality was consistent and satisfactory, the buttons were intuitive, and the price is right. We also liked the $100 LG Electronics HFB-500. Its call quality passed muster, but we were more drawn to its environmentally friendly aspect: Except for the very first charge (for which you must use a wall socket), the HFB-500 can obtain all the juice it needs from sunlight-you just need to live in an area where the sun shines regularly. (The $100 Iqua Vizor Sun is also a solar-powered unit, but it didn't rank as high as the LG model because of inferior call quality.)

Talking on a speakerphone-and not with an ill-fitting headset-certainly makes a 45-minute conference call on your evening commute much more manageable. Nevertheless, you should be prepared for a couple of drawbacks. First, most speakerphones have illuminated buttons or blinking lights, and their flashing can drive you nuts, particularly at night. Second, leaving the speakerphone perched in your car is convenient, of course, but-depending on where you park your wagon-you run the risk of drawing the attention of thieves. (And if you are thinking about purchasing a windshield-mounted unit, remember that it may be illegal in your state to attach any device to your windshield.)

Lastly, for your Bluetooth cell phone to play nicely with a Bluetooth car kit, your phone needs to support both Hands-Free Profile (HFP) and Handset Profile (HSP). For more information about Bluetooth standards and profiles, and for advice on how to choose the right devices, read our Bluetooth products buying guide.