Thermoelectric power generation for low pwerr wireless transmitters a step nearer?

Thermoelectric generation has been around for a long time, and can be found in active use - it just is terribly inefficient, so "micropower" is about right.

As best I recall the Russian army has kerosene lanterns with TEG built in. Light up, get a little power. There are also much larger thermopiles in use for things like remote cell sites where the lack of moving parts (.vs. a mechanical generator) is deemed worth the much larger fuel supply needed for the same power, when long-term unattended operation is required.

There is also the thermoelectric fan that sits on top of your wood stove, in commercial production - you can buy one rather easily.