Lets first congratulate the research community on this achievement. Application oh human body is part of the story, you can use these tiny generators in several other places.
@Feory scary thought haan :).
Just think, if people have wirelessly connected nanobots traveling through their bodies, transmitting and receiving data, then maybe a "virus" attack on the nanobots could produce symptoms like an actual virus in the human host!
I feel these robots will initially be tried out on patients who are significantly ill. No relatively healthy individual will readily agree to have implants in her person just to enable doctors make clinical measurements.
This effect should enable the industry and regulators determine whether the technology is safe.
The FDA, and for that matter the FCC, need to get into the act to address the safety and communications protocols for all this nano stuff in my body. Placing foreign objects inside humans may be beneficial as long as nanorobots can recognize each other in the blood stream and communicate coherently with the outside world, and among themselves.