Ideas
+41
EKG electrodes or stethoscope for heart rate monitoring
Since the Rack includes a heart rate monitor which shows the subject's heartbeat, perhaps the subjects could have EKG electrodes attached to their chests or a stethoscope chestpiece strapped to their chests to show just how their heartbeats are being monitored.
Customer support service by UserEcho
Well, the subjects have a chip thing on the backs of their necks, you can see it with the free camera, that's probably how they're being monitored