3D printing accessories like liquid print heads, laser cutters, and continuous production thing that I call a "broom". Android based robotic rovers (we were the first to do one at google i/o 2010, I should do a writeup on how that went). Industrial control systems.
Thats really cool. How are people (the few that do) currently buying your products? How do they find out about them?
Paypal, and... that's the thing - I don't want to spam. I did an indiegogo last year, but I have no idea how to advertise in a non-spammy way.