Never seen those before amando, they're new as of this year, nice though. I wonder at what niche they'll fill though, anything powered by a single alkaline or NiMh battery is going to be pretty cheap.
Personally I think it's easier to just use a single lithium cell. They'll run any conventional low voltage cmos IC's, they're not difficult to charge and are very safe and affordable now.
I've made joule thieves before, and I find little they're useful for that couldn't be made easier using the proper voltage cells other than units that can make an LED glow by taking the last bits of juice out of dead batteries. They're more novelties that useful.