Sympathetink is a great little package. Mathieu Bich is a super creative guy, and he really knows how to utilize current technologies!
I love these pens, I use them all the time for little touches like adding visuals to predictions, or reveals or whatever.
The beautiful thing is, the pens are quite readilly available (at least they are in the UK anyway!), so if one runs out- pick up another for a few quid!
They're great for pranks too!!
CL