Headset makers handle the arrangement and feel of the function buttons differently, too. Some buttons are recessed, others are raised, while still others are flush with the headset's surface. Some buttons sport notches or markers; others lack indicators entirely.

In-car speakerphones: You'll find plenty of Bluetooth car units--from companies such as , , , , , and Plantronics--that are portable and ready to pop into your car. Expect to pay about $20 or more for an entry-level model or an older unit; from there, prices can go up to $100. You position the speakerphone unit on your sun visor, your windshield, or on your dashboard. (Note: In some states it is illegal to attach any item to your windshield.) In addition to managing calls, some speakerphones let you stream music and transmit audio through your car stereo.

Many brand-new cars have Bluetooth kits factory-installed. If yours doesn't, you can have a professional wire up your car with a speakerphone.

We'd like to say that these days call quality through a Bluetooth headset or speakerphone is consistent and comparable to--or better than--what you get from a cell phone on a good day. But it isn't. In our testing, even the best-sounding headsets overall still had their off moments, producing faintness, voice distortion, echoes, and disappointing background-noise cancellation, for example. And judging from our tests of car speakerphones, their audio quality is even less impressive. Interference of various kinds made a regular appearance. Car kits don't handle background noise as successfully as mono headsets do, either. Furthermore--and not surprisingly--voice commands ("Call Julianne mobile," for instance) work considerably better when you're wearing a mono headset, since the attached microphone is positioned close to your mouth.