Comment by farkanoid

Somewhat related - I've been working on a design using Nordic's NRF52840 SOC for work; Intensely focusing for the past few weeks on antenna tuning for maximum BLE range.

Part of the testing involves using the 'nRF Connect' app, which lists all nearby Bluetooth devices, plots signal strengths, and allows for some rudimentary communication. It doesn't seem to be Nordic-specific.

I'd frequently leave the app open scanning during development late in the evening, and rarely, an unidentified Bluetooth LE device would pop up for a few minutes then disappear.

Turns out it was my dad's pacemaker, which sends telemetry via Bluetooth to a 4G gateway they gave him (this only happens after he lies down with little movement apparently).

This prompted me to look into pacemakers and deactivation after death of course. I wish I hadn't, it turns out they leave it in the corpse unless it's scheduled for cremation.

Because of the aforementioned research, and the open field tests I was performing, it somehow devolved into me having a nightmare where I was RF testing at a graveyard, and the app suddenly displaying a bunch of pacemakers underground.

...I really hope this isn't possible - The signal through 6ft of dirt and concrete would be marginal but still detectable.