- Nuclear-powered electricity source

- Touted as a "battery"

- Solid state

- Can be cooled by heatpipes and ambient air

- Can use multiple fuels

- Cheap

- Small

I'd bet dollars to doughnuts that they're commercializing a Radioisotope Thermoelectric Generator (or multiple connected in a series), like the ones sitting abandoned all over the former Soviet Union (and occasionally spewing radiation when some fool disassembles them for scrap metal)

http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_gen...

Note that it's also touted as "Always On", probably whether you like it or not, because you can't switch radioactive decay on and off.