Cheap wireless systems are rubbish, the only system that is ok is the Clarion system but is not cheap. You will have a far more reliable system if you hard wire it. Most of the cheap wireless systems suffer from cross imaging, so if you are in range of another wireless camera you can get their image not your own. They also suffer from interference when near other RF signals like uhf radios, wireless internet, remote garage doors ect. The Clarion system is Bluetooth so the monitor pairs with camera, so lot less interference.