Until the 1980s, you had almost nowhere to put your cup while you were driving. So the automakers started the cup holder wars, adding cup holders everywhere. Then, after the iPod was released, scores of companies started making accessories, with one of the most popular being the car FM transmitter, a device that would plug into the hole that used to be your cigarette lighter to send music from your iPod to your FM radio, so you can listen through your car speakers. In general, this means better sound, and it means everybody in your car can listen to the melodies.

So it would seem inevitable that a creative engineer would combine these two heavy desires and create an FM transmitter that fits in a cup. Not only do you get to listen to your music; you also have a handy place to put the device where it won't get in the way -- at least not if you have enough cup holders in your car. The BTCUP from Macally is a $99 device that sits steadily in your cup holder and connects your iPod, MP3 player and even cell phone to your car speakers.

I have had the opportunity to use a number of different FM transmitters. While some have excellent transmission capabilities, I always find myself hanging them awkwardly. They seem to be in the way when driving or trying to tune the radio. But not so with the BTCUP, because it has its place in your car -- and it doesn't move.

The key to the stability is the way its base expands and contracts to fit the cup holder. Squeeze it to fit it into a small holder. Let it expand to fit the larger holders. It's spring-loaded so it lightly holds itself into place -- avoiding the tipping that might happen with your 32-ounce big gulps in the same spot.

The FM transmitter is competent, although like most FM transmitters, its sound changes in varying environments and depending on where it sits in relation to your radio and radio antenna. For instance, while driving through a tunnel, the sound quality may diminish. That also means that you'll probably determine which cup holder sounds better than all the rest. I like the BTCUP's quick scan button that finds an open frequency. I don't know how it knows a frequency is open, but it's faster and easier than manual tuning.

The Bluetooth feature also allows you to use the BTCUP as a hands-free interface to your cell phone. Your voice is picked up by the built-in microphone and you hear the other party in your radio speakers. If you own a fancy car with similar features, this might not thrill you, but for $99, it goes from car to car with you. Dialing a call and connecting your phone automatically switches the sound to your phone and turns off the iPod music. This feature doesn't work with non-iPod MP3 players because they use the same Bluetooth port as your cell phone.

If you're an iPod user, your iPod will sit nicely on top of the BTCUP, attached by the metal and plastic port. It charges your iPod while you play. Your phone, with its Bluetooth wireless connection, doesn't need to sit on top of the device. Other MP3 music players connect the same way as the cell phone -- so they need to be Bluetooth ready to use with the BTCUP.

If you need the transmitter for only iPod and no cell phone or other MP3 player, you can opt for FMCUP, a non-Bluetooth version for $59.