Do not receive the 666 mark

VeriChip : an implanted device used for identification by a third party.

VeriChip was a human-implantable microchip. It was marketed by PositiveID, a subsidiary of Applied Digital Solutions. It received United States FDA approval in 2004. Its manufacture and marketing were discontinued in 2010. About twice the length of a dime, the device is typically implanted between the shoulder and elbow area of an individual’s right arm. Once scanned at the proper frequency, the VeriChip responds with a unique 16 digit number which could be then linked with information about the user held on a database for identity verification, medical records access and other uses. The insertion procedure is performed under local anesthetic in a physician's office.
From Wikipedia

US Patent 5,878,155 : Method for verifying human identity during electronic sale transactions.

Granted by the US Patent & Trademark Office on March 2, 1999.
Abstract: A method is presented for facilitating sales transactions by electronic media. A bar code or a design is tattooed on an individual. Before the sales transaction can be consummated, the tattoo is scanned with a scanner. Characteristics about the scanned tattoo are compared to characteristics about other tattoos stored on a computer database in order to verify the identity of the buyer. Once verified, the seller may be authorized to debit the buyer's electronic bank account in order to consummate the transaction. The seller's electronic bank account may be similarly updated.

US Patent 5,629,678 : Personal tracking and recovery system.

Granted by the US Patent & Trademark Office on May 13, 1997.
Abstract: Apparatus for tracking and recovering humans utilizes an implantable transceiver incorporating a power supply and actuation system allowing the unit to remain implanted and functional for years without maintenance. The implanted transmitter may be remotely actuated, or actuated by the implantee. Power for the remote-activated receiver is generated electromechanically through the movement of body muscle. The device is small enough to be implanted in a child, facilitating use as a safeguard against kidnapping, and has a transmission range which also makes it suitable for wilderness sporting activities. A novel biological monitoring feature allows the device to be used to facilitate prompt medical dispatch in the event of heart attack or similar medical emergency. A novel sensation-feedback feature allows the implantee to control and actuate the device with certainty.