If it's very thin, then I think you might not really feel anything.
I'm more worried about the fuel cell having some negative affect on your blood as it runs through it though. ;x I don't really have a basis for my worry, it just seems a bit too good to be true to me. I do find it fascinating though.
I wouldn't like to idea to have an ID chip in my body, and I wouldn't like to idea of having this thing in my body. Although the concept is pretty cool, I just seriously wouldn't like the idea of having something like this connected with my veins.