The word Telemetry is derived from Greek roots tele = remote, and metron = measure.
Fulcrum Designs has developed telemetry in all manner of devices, most recently the Fulcrum Navigator system. This collects, collates GPS information and adds further data at the transmitting end of the link and sends it to be further worked on by a radio receiver for display and eventual action by the user at the other.
Typically telemetry information might be temperature, depth, position, voltage, current, speed, pressure, humidity, light intensity, G force, rotation, yaw, pitch, altitude etc.
Data may be sent in real time or stored and sent in bursts.
The link can be hard wired, laser, microwaves etc, but is normally by radio.
Radio links can be low powered short range (200 metre) or global via mobile phone networks.