Don't get those all-in-one package security cameras that include a camera and a monitor. That's not what you want. You need to piece it together yourself by buying separate cameras, modulators, and video signal splitters/splicers. The cameras can be simple and cheap. I like this one since it's cheap, weatherproof, and very unobtrusive. You'll find a bigger selection here .
For modulators, check the selection here . Keep it simple. You don't need stereo. Indeed, you may not even want audio. You'll need a modulator for each camera you get. There are some 3-in-1 and 4-in-1 modulators that may suit you better if you plan on mounting three or four cameras. They can be expensive, but they simplify wiring.
Basically, you mount the camera, run the wires from the camera back to the power supply and modulator, set the modulator to the channel you want the camera video to be on, and then splice the modulator's output into the home's antenna cable or UHF/VHF-tunable cable line from the cable company. You may need one or more video amps to do load balancing between the modulated camera signals and the antenna/cable signal.
I'd recommend not getting the wireless cameras. They work great, but they still need a constant supply of power and may interfere with some 2.4GHz equipment. Also, you're severely limited in how many of those you can have within close proximity to one another. The last one I looked at had only two channels, so you could have a maximum of two cameras on one property.
After you get your cameras and modulators in place, do you plan on recording anything, or do you just want to be able to view it in real time?
If you want to get good equipment, definately don't buy the "ready made security system" deals you can buy at Sam's Club, or elsewhere.
I was formerly Director of Security for a corporation, and I bought all my equipment from Direct Low Voltage Supply. They are a box house, and their prices cannot be beat. Their equipment is professional quality. http://www.directlvs.com/
You can get 3 or 4 good cameras, and a switcher. Call them up, and they can help with anything you need. And no, I have no vested interest in the company. They have always treated me right when I was purchasing equipment.
Kansas City, MO
Home theater photos located at http://home.kc.rr.com/thetennisons/