Turning the Cold of Night Into Electricity

This story's all over today, but in case you missed it, here's a decent article at Vice:
This $30 Device Turns the Cold of Outer Space Into Renewable Energy

It's flea-power, but still it's pretty neat.  I wonder if it'll run a QRP radio?  Correction, I wonder how long until Peter "not Spiderman" Parker uses one to power a home-brew radio and talk half-way around the world?

Seriously though, I wonder how many milliwatts this puts out, and how it will scale, what are its limitations, and a bunch of other engineering questions.  Still, even if it goes no farther than lighting a single dim LED, it's a cool (heh) demo.

ps: Here's the original paper.  Current power output is approximately 25 mW/m^2.  For comparison, this is about 1/10,000 the output per unit area as a modern production solar panel.  Or, flipping this around, it'd take a about football field sized device to run one conventional 100 Watt incandescent lightbulb.  Interesting, but of specialized, limited use at best.