Jupiter Jack, "the most convenient hands-free cell phone device," according to the Web site video, uses an FM transmitter and your cell phone's headphone jack to send a caller's voice to your car radio when it's tuned to FM station 99.3 or 101.3. "Just plug it into any phone and mount it on the dash," the video says, and it "transmits quality sound through the speakers in your car." We paid $23.98 for two devices, including shipping. A car mount for your cell phone is free, but shipping is $6.99.
We had a couple of our testers use Jupiter Jack on their daily commute and on weekend drives through suburbs and cities.
Redial. We got a usable signal only when at least one of the two FM stations was clear. That's most likely in a rural area. You'll have to experiment with phone placement, since the phone is still needed to pick up your voice. And someone nearby with an FM radio could pick up your conversations. There's good news for those who have trouble hearing: Because Jupiter Jack uses the car radio, you can crank up the volume. It's best never to talk while driving, but if you must use a cell phone in your car, consider a good Bluetooth headset, which should work better and is really hands free.