whats "half decent" ?
size, pixels etc...
im sure you have to have the aerial on some makes stuck all over your glass (just like the rear windscreen lines) then is obvious to every theif you have a TV unit :\
i dunno really mate, ive never looked into tv signal. i only had a screen, and hooked it up to ps2
however, alpine/pioneer seem to be the kings. many other makes now (rip speed etc) that are far cheaper, but they feel cheap and you really have to focus hard apparently