I should have mentioned this as well and you may even know about it. There is new technology out with Voyager called WiSight. This is a digital signal type wireless system that only the camera and monitor are compatible together, this eliminates interference that you can pick up and increases the range that the analog type systems are noted for. WiSight has a range of 60+ feet through objects. This link Voyager Systems & Kits
has some more info on this as well. Follow the links to the U Tube videos on the systems as well.