Current implantable devices, pacemakers, artificial hearts, etc., store data on their operation.
Not to say this couldn't be abused later, but by itself, this is nothing to get the willies over.
....And soon, right after health care probes get inserted, we'll have sattellite traffic control accounts in order to drive cars. Driving infractions will be detected by land based sensors and fines deducted automatically by sattelite communication from your account
and a bio-probe inserted in your body will administer penal justice in the form of Tax Shock Therapy as deemed fit by the Traffic Ministry
no biggie, its just change
Unless you are a dog:
http://www.prisonplanet.com/chipped-pets-develop-fast-growing-lethal-tumors.html