I can’t say I’ve ever suffered from cold knees whilst working but it’s good to know that if I ever do get struck down with such an ailment there is a USB solution, Warmmi USB Heating Knee Pads.
I’m guessing that the Warmmi would also work on cold elbows, another occupational hazard of all bloggers.
Further info and available to buy from vavolo for ~$20, thanks Cassily.