Your heartbeat may not be as private as you think.
In July 2013, U.S. Patent 8,478,418 was granted for a "Remote Health Monitoring System," designed to monitor a patient's body from a distance.
The patent describes sensors worn on the body that continuously stream heart, breathing, and movement data to a remote server in real time. When the server flags something, it reaches back and pulls the detailed recording stored on the device.
But there's an important catch: a patent is not proof a device was built. It does show continuous remote body monitoring was formally documented and patented.