Setting aside any SmartThings issues, the technology has been around for years and works just fine. 
probably most widely used by
Enocean. The idea is simple: when you physically push a switch, you are generating just enough energy for a tiny microsecond radio burst. Zigbeeâs âgreen powerâ profile allows for messages as short as 2 bytes, and thatâs what these switches are using. No battery required. 
Zigbee PRO devices using the Green Power feature are able to complete communication with an average 100-500 ÔJ (micro Joule) of energy. This energy is often created by capturing the energy used to flip a switch via common energy harvesting techniques including piezo-electric elements and dynamo/electro-mechanic converters.
https://zigbee.org/zigbee-for-developers/greenpower/
Note that the green power zigbee switch is not powering the light itselfâthat would take a lot of energy. Instead, itâs just, very briefly, communicating with the zigbee network with a tiny radio.
So science, yes. Fiction, no. 