Poon’s team developed a new type of near-field wave that propagates through skin and body tissue, rather than be reflected like longer wavelengths or absorbed by like typical near-field chargers. The wireless charging emits waves at roughly the same power levels of a mobile phone, and is therefore deemed safe for use.

The researchers demonstrated the power delivery technology in a pig and a rabbit, which had a tiny pacemaker fitted solely powered by the wireless technique.

Actually, the breakthrough seems to be in how to give it power:

They can be charged using a device the size of a credit card placed outside the body.

"With this method, we can safely transmit power to tiny implants in organs like the heart or brain, well beyond the range of current near-field systems,” said Dr John Ho, co-author of the study that appears in the Proceedings of the National Academy of Sciences.

...

The discovery opens up greater possibilities for medical implants called “electroceutical" devices, which use electrical stimulation to treat illness or alleviate pain that would typically require longterm drug treatment. Diseases like Parkinson's are already treated with techniques like deep brain stimulation to control shaking symptoms.

Beyond medical devices, one of the largest stumbling blocks to embedding computing devices and sensors in the body has been supplying them with power. With the ability to power them the possibility of embedding fitness trackers, biosensors such as heart rate, blood glucose and hormone monitors, or any other small electronic devices within the body has been opened up.

This is very cool. Thank you for sharing this, Geege!