A tipital set-up would be (for three cams) similar to this.
3 cams
3 motion sensors
1 transceiver (converts the Radio Signal to x10 house wiring signal).
1 VCR commander II
Maybe a wireless video sender and receiver (with sound if you want sound).
Set the cameras in the same group of 4 (that means if you use house code A you would use number codes 1, 2, and 3.
set the motion sensors to trigger the cameras and the VCR commander II
The cameras (I am assuming) have the code addressable power units. When one turns on... it turns off the others in the same "group of four".
I use an auto-switching video modulator for my cameras they all feed into it (up to four) then I can send the video via a video sender or even coax. I have a plan to tie the cams into the cable system.
Of course, the scan pad remote would be fun too.
Before doing much of anything read more at this forum. And read the PDF(s) how-to guides for any products you considers. I click the "whats included" links to see the glides.
Plan your project carefully, be flexible, and have fun.