Fitness technology has come a long way in the last few decades. Apps and devices are available to measure just about any piece of fitness data imaginable. It hasn't been that long, however, since the world's first heart rate monitor was introduced.
Micro Heart Pulser
In 1977, Polar introduced its first fingertip heart rate monitor, the Micro Heart Pulser, which was used by the Finnish cross-country ski team as a training tool. A user held a fingertip to the device and waited for a readout. The Micro Heart Pulser was the world's first EKG-accurate heart rate monitor.