The basic thought here is that there's a ton of energy in our environment, specifically in the form of high-amplitude RF waves from TV broadcasts, and we should be able to use that energy to do work.

This project is trying to figure out what the equivalent of an rfid tag looks like with that power model. They come up with a scheme of being able to absorb versus reflect the ambient signal to communicate between unpowered tags. Maybe the most productive way to think about this is as a step into the larger research area of how to effectively harvest energy and do useful stuff with devices that don't need batteries.