This story describes a patient idenfication system implemented to reduce the incidence of operating on the wrong patient.

To help prevent similar mix-ups, Birmingham Heartlands has installed a
patient tracking system in its ear, nose and throat ward. Developed by
Safe Surgery Systems, the system uses radio frequency identification
(RFiD) tags in plastic wristbands to monitor patients' progress through
the ward. Patients are tagged on arrival and given an RFID-equipped
wristband. A digital photograph is taken and attached to the electronic
patient record to help confirm identification. The tags are passive -
they have no battery, making them slim and light, and are only
activated when they pass through an electronic point emitted from
antennae placed around the ward. Each tag can hold 170 pages of data
and is discarded after use to prevent the transfer of hospital
infections such as MRSA.

It seems that bar codes would accomplish the same thing at significantly lower cost. The one advantage this system has is that the RFID tags are automatically read when they pass through choke points - but human intervention is still required to establish context so that the system can determine if the scanned patient is the one scheduled for surgery.