[bigyikes]

What about a wireless receiver instead?

I have some smart light switches in my house that don’t contain batteries and aren’t wired to mains. They’re powered purely by the force of pressing the switch. A bite-powered receiver might not even need batteries. Okay, maybe I’m getting too crazy?

[lisper]

A receiver that size is borderline trivial but extremely risky because the transmission could be detected.

[InsomniacL]

what about powerless?

https://en.wikipedia.org/wiki/The_Thing_(listening_device)