The doctor came by my place to give me a physical in support of an insurance policy my company is taking out on me (I'm now probably worth more to them dead).
This included an ECG, all portable and battery-powered; he stuck a handful of electrodes all over my torso (I'm hairy: taking them off hurt), plugged them into his machine and it tracked my heartbeat for a few seconds. Then he called up the lab, read my identification off to a person there, and held the phone handset up against the ECG machine. It whistled a (loud) tune into the receiver for maybe thirty seconds, then the doctor got back on line and the lady at the other end assured him that the ECG was normal.
I was flabbergasted, wafted back to the days of 300-baud acoustic couplers. Then I was flabbergasted again (given the presumably low bandwidth of this way of doing things) how little information is required to represent my living beating heart.