Abstract: A system for monitoring a condition such as tire air pressure where the monitor at each tire is remotely energized by radio waves, there being two embodiments disclosed for effecting this. A loop antenna concentrically mounted with respect to each tire receiver and/or transmits electrical energy to the remote location which is typically at the operator's console. Each pressure sensitive device is mounted away from the valve stem and may include a strain gauge mounted on the tire side wall or between the wall and rim. An infra-red detector may also be employed as a pressure monitoring device.