Why would you have to buy a second Palm unit?
You can use the same Palm device you're using for other things. As to the cable, it's a standard HotSync serial cable. You can get it from any store that sells PDAs.

Future plans include downloading the playlist directly from RioCar without HotSyncing! BTW, that was my original plan, hence the refresh button, but it was not reliable. I'm still working on it.
Another thing of course, is add GPS capablities. I was thinking about connecting the GPS device through an AB serial switch. The user would have to select which connection to use.