I too am part of the energy harvest challenge. Unfortunately I don't have my kit yet but according to tracking number it got to Australia last night so will hopefully get a hands on play Monday or Tuesday.
My original plan was to hopefully monitor my homebrewing process with it. I'm doubtful I will be getting enough heat from fermentation and CO2 emissions to monitor everything off that but will be looking at things I could do to harvest power from grain till the keg. The other key thing I will have to do is find sensors for measuring everything that are passive or use as little power as possible.
Key things I want to measure temperature wise:
Mash temperature: good 30 degrees or more temperature differences so should be ok here power wise.
Time till boil.
Time to cool: will I be able to store enough temperature?
Fermentation temperature: will not be a big temp difference I know this thing can run of body heat but wonder if I will have enough to do the occasional read out and as the brew ages the difference will get lower.
First step is just logging how much power I'm harvesting off each stage. After this will want to try and add on more sensors to measure things like ph and specific gravity at different stages but we will see how we go.
I'll also be looking at other areas I would like to be collecting data that it is either to far away from power or just freeing up a power point that isn't needed.
I'll do something a bit more in depth when my kit arrives next week and I have a bit more of an idea of what I can do with it but I'm sure it is going to be fun.