Implanted microchips have long been used in the animal kingdom, to track wildlife and to help pet owners recover their lost animals, but the idea of using them on humans has sparked fierce criticism from scientists and privacy advocates alike.

Applied Digital Solutions Inc. says its glass capsule the size of a grain of rice, injected into forearms and other fleshy body parts, could help authorities find missing persons and speed up medical diagnosis treatment.

The VeriChip, a scannable device worn under the skin and encrypted with personal information like medical records and emergency contacts, was unveiled last year in Florida.

So far about 20 people have been “chipped,” including an entire family in Florida.