[ChuckMcM]

I'm surprised they don't mention methane. Given that a natural byproduct of e.coli is methane as it reduces organic waste in your intestine, a fuel cell which could transfer oxygen from the blood and methane from the bowel would potentially generate milliwatt or two. As I recall there was some work on a methane recapture facility for grazing animals as a way of powering remote monitoring as well. Easy to joke about too, "Honey, pull my finger, I need to charge my phone."

[Retric]

Messing with the gut is really dangerous, your probably far better off just harvesting some sugars from the blood stream than trying to use methane.

[jononor]

Messing with the blood is not danger-free either. Wrong blood-sugar levels or acidity, bloodclots, gas-bubbles...