I am going to add a rear view camera, and headrest montiors, when in reverse will the headrest monitors show what the camera sees?

It depends if you have your headrest monitors hooked directly to your monitor or to a seperate Video source ie a ps2 or some other DVD player if they are hooked to the Rear Video out from your monitor than yes the headrest monitors will show your back up camera view.. Does this make sense.

I meant the camera is hooked up to the f90-bt and then the monitors are hooked up to the rear video port on the f90bt

yes they will still show up on headrest monitors then..

hmm well right now there something wrong with the connection to the headrest monitors (theres at least 100+ wires behind my avic, mushing them back there something mite have gotten disconnected) :/