I have many intertwined ideas for this. The simplest one would be to have a reader that you press a key fob ibutton to and the empeg could then identify you. It could be tied to wendy filters, playlists, volume, etc. I think that there is some support for one-wire built into the empeg. I read something about the built in temp sensor is a one-wire ds1820 chip.

I should point out this is total vapor at the moment. I have worked with one-wire chips and weather stations under linux, but I haven't yet sucessfully built an empeg kernel. You can read about one-wire/ibuttions at www.ibutton.com.

other ideas I have:

tie it to the ignition system. so no ibutton or no empeg, and no car start.
have it linked to my NO system so only people with authorised ibuttons can use the nitrous.