I did some work with his Greenarrays chip as a student. It was very limited and awkward to use but it could also operate on absurdly low energy, with very low o

I did some work with his Greenarrays chip as a student. It was very limited and awkward to use but it could also operate on absurdly low energy, with very low overhead for waking up or almost completely powering down. At some point, we had a demo running some simple signals processing code off a homemade bleach battery, and I wouldn't be surprised if you could make something work off a bunch of lemons too. This was over a decade ago (yikes) and I don't remember the exact numbers, but I do remember it used substantially less power than a comparable MSP430 microcontroller. That seems pretty useful and impressive to me, especially given it was created by a very small team with limited funding.