i got this thing that looks a bit like a toothbrush handle married with a screw driver for FREE from one of those tupperware kiosks at a mall - it's basically a citrus "zipper". has a little wedge shaped inset, that's just sharp enough, and deep enough to score lines around a citrus item, and then the peel just comes off. kinda neat to do in a spiral, and then you just go zippppppp.

yours looks intriguing though, i'll have to check one out sometime.