I'm not sure If you want to record yourself but if you want to record others use a hand held and it can go in the headphone socket. But I would be guessing you would want it of the intercom. You could use the one from the back seat and only use the headphone one as the intercom will do the rest. I might be wrong but headphone is normal 1/4 inch and therefore you need a line cable plus a jack. no connection but this sort of stuff
http://www.trianglecables.com/35minsterfem.html
http://www.trianglecables.com/2footminster.html personally I woukld use a MD recorder so much better quaity butonly sony sell them and only one at £200ish
Hope this helps
Dave