I recently tested out the Orbyx FM Transmitter for iPhones and iPod. For those that don't know what a FM transmitter is, well I'll do my best to explain.
It's a fairly simple device and easy to use. All you do is plug it into the port on your iPhone or iPod. You then either automatically scan for stations or you can manually select one. You then tune your car (or any radio I assume would work) to the same station and whatever audio is playing on your iPhone/iPod will now play over the radio.
This is especially handy if your vehicle doesn't have a way for you to connect your iPod to it (which is mainly older cars). All you need is a radio!
The Orbyx transmitter works well. Though for some reason the station has to be changed at certain points on my journey to and from work. Its usually the same points along the trip what I have to do this. Maybe the radio frequency dies out at this point. But luckily there is a 4 station memory that makes it easy to switch between stations with ease allowing for uninterrupted listening!
I recently let a friend try it out to see what he thought and he loves it! He told me that he is actually doing better at staying up to date on all the podcasts he listens to. As he used to listen to them with one earbud in while driving.
If I'm right about being able to use any radio (and I don't see why you couldn't. I'll have to try and update this later.) then this device could be very handy for parties. Say you have all your music on iTunes, have a nice big stereo, but no way to connect your iPod to it to play the music for the party. Use this and your nice big stereo becomes your private radio station! Playing what you want, when you want and using the big speakers of your stereo as opposed to the little ones on your computer.