The Greener Gadgets Conference had some really 'interesting' concepts. Take this concept by Jim Mielke for example; a gadget that is 'tattooed' under your skin and runs on blood by turning glucose and oxygen into electricity.
It's an electronic interface embedded under the skin that looks like a tattoo. You could use it as a phone, computer, or traditional tattoo by loading it up with a new tattoo design whenever you get bored. The display "works" by changing the color of smart-ink pixels tattooed over the implant. It also acts as a touchscreen input device, so you could manage your cellphone calls by tapping on your arm. There's also potential for a 3G video call to be shown on your skin. This would probably be a bad idea on really hairy arms!
Check out more stories from the Greener Gadgets Conference: