A system for monitoring physiological parameters within the stomachs of ruminant animals and including two primary interdependent components. Both components are linked by radio frequency communication and software designed specifically for this application. The first component is a sensing transceiver, battery power and electric components hereafter referred to as the device that is tethered by a cord to a weight in the form of a conventional cow magnet. The second component includes both stationary and portable readers/transmitters capable of initiating radio frequency communication with the device(s) for receiving data from them and sending data to them. Software residing in both components utilizes digitized data and operating commands for transmission between the components, for storing selected data and program commands and manipulating the data for viewing, hearing and related analysis.