Your Pioneer does have a video out RCA on the rear of the unit. For the TView monitors, this will depend on what they actually are. Are the units strictly monitors or DVD built in (if built in, is there a DVD player in just one or both of them?).
Are these factory headrests retrofitted with separate monitors and external DVD, or full replacement headrests? They will have an input option most likely in any configuration, but the wires may be missing or hard to get to. If the installer only intended them to be used with their own player (assuming they have DVD), the separate harnesses with audio/video input RCAs may have been left out altogether. If you can provide the model number of the units, I can get you more detailed info.