It is just a cheapo FM transmitter - plug it into the power port, insert a USB thumb drive loaded with MP3 (think it does other formats too) files, tune into any of the 7 FM channels from 87.7-89.1 MHz with no local signal on it and off you go.

I got mine at Target and figured it wouldn't work worth a **** but I was wrong. It actually has a pretty good sound, especially when the MP3 is from a clean source. Some of the ones I downloaded off Napster way back when are a little noisy but they weren't clean to begin with.

Only drawback to this thing is it will only play the tunes in the order they were copied to the chip, you can't shuffle. But it does have a skip button so I just jump ahead to where I want to start.

In most cases the signal is strong enough to overcome any local radio station - I use 87.7 from my house to work which includes going through downtown Boston.