Almost all after market CD head units should come with an auxilary capability, this is where the reciever would go.
They use to be "line of sight" only, but now they have ground based re-transmitters that are stationed around the country.
The $10 means you don't have to listen to those ******* DJs that think you want to hear their voice at 8AM during your already stressfull drive to work or where ever.
You also get a far better range of music on each individual station, with each station being the same as radio - Country will play country, rock will play rock, and then they are broken down into categories.
The reciever has the capability to browse categories, and shows what songs are currently playing on each station with the artist listed. They also don't only play mainstream stuff, which is mostly crap anyway, so you get a much better choice of music and the music isn't limited to "radio approved" types. Instead of a cut down version of a certain song, its full length. It also has a significantly better reception, and when driving far distances you don't just start losing the station and then have to drive through a area completely void of any worthwhile radio stations.
Theres also no commercials, and only the occasional "You are listening to [whatever station]" - but most importantly, for me anyway, is no ******* DJ talking. Man I hate those *******s, they just talk and talk and talk. I don't want to listen to those *******s, why does anyone want to listen to those *******s? They are more annoying than I am!
Anyway, its worth $10/mo if you like to listen to music rather than hours on end of commercials and some ******* DJ talking.
-SW