microgeneration could be useful to power wireless networks and sensor devices to provide data for building automation control systems. Here is an example where microgeneration is applied to biotech devices.
In this story from MIT Tech Review:
A team has shown that they can generate power (~6.5uW) from a fuel cell embedded in the tissue of a rat. The fuel cell uses glucose from the bloodstream to generate power.
A pacemaker requires ~10uW of power to run so this is not quite ready for prime time but it suggests an approach that makes embedded medical devices much easier to live with (no external battery packs or replacement needed).