So you want to be a transhumanist grinder? These are some implant types you might consider.
The following are transponders. 
Responds to any reader that creates an RFID field, it will return a long ID, suitable for identification purposes.
Similar a finger print reader, except you have to remove the chip rather than burn off your fingerprints.
As above, except you can rewrite the chip to display a different ID from time to time. (Limited amount of rewrites?)
Passively powered as before. Can hold a bunch of custom data and has some compute ability such as password protection.
Compatible with NFC smart phones. Shiny
The next gen are are smaller: 
You can stick them on your nails rather than implant them. 
How do they work?
It's getting hot in here.