igargoyle reader, Robert pointed me to WarmX, a company that produces undershirts that have a panel of heating fabric. I originally heard about this early last month, but was sparse on details. The idea is simple, but their fabric won't short circuit, is washable (as one would expect), and produces seven percent of a body's heat. The panels are located around the kidneys, and the batteries for the warming fabric last from 2.5 hours to 4.5 hours, depending on the setting, and recharges in three hours.
I live in Los Angeles, so usually staying warm isn't a big concern for me, but I could imagine that this would be pretty useful for going out to the desert or visiting colder parts of the world.
Here's a link to their store. They're selling undershirts for € 258.00.
[ Link via Robert. Thanks Robert! ]