Energy Scavenger - I remember when .. ..
As an exercise in "green" electronics, some 40 years ago, I built a two tuner radio using low power transistors, the first tuner was used to hunt for a signal strong enough to put static through a crystal earpiece - and was normally Long Wave Radio 2 , the second tuner was then used to locate the station I wanted to listen to.
For extra boost the aerial could be crocodile clipped to a wire fence / frame ( such as a bed frame ) and provided free listening almost anywhere. It was also built from Balsa wood about the size of 20 ciggies.
I live in a city saturated with WiFi provided by a Telecom providor, so it would be quite feasible to suck all that free energy instead of hunting for a radio broadcast station.