I'm curious because the last time I surveyed the literature of diy implantable devices there didn't seem to be anything on a power source strong enough for a bluetooth device to operate for hours at a time.
There are, lithium batteries. The problem is, they outgas and explode. People do not want to implant these batteries, even with a low failrate and detectors.
There were things, e.g. the NorthStar implant, which became EmbediVet. But for aforementioned safety issues, it wasn't even used for cows.
Passive tech is the only thing right now (RFID, NFC)
