I've recently been looking into cheep displays for various projects including retro computing and i came across the TVout library for the arduino. it looks pretty promising so far. I am finding that these car TVs are getting dirt cheep now (probably because they are getting replaced with phones and ipads) and i got two for $10. aside from the arduino I havn't spent anything and since iv'e already got one i'd say it's a write off as well. all it took was a jack, two resisters and some wire for the circuit. you could easily build a standalone board with an ftdi chip for a couple of dollars and there's already a sample program for serial terminals.
