They are available but you’ll have to hunt for implantable chips. VeriChip wanted to chip US soldiers to replace dog tags. The Mexican government uses them in a few high security programs. GPS isn’t yet small enough for incorporation. You can always use chips available for pets. A fair number of hospitals use RfID chips in bracelets. Readers at stariwells & elevators tell the system when someone leaves the floor/area. Alsoused to verify prescriptions, etc.