With USB charging and multiple temperature levels, these compact hand heaters keep my palms and ... After all, a hand warmer is basically a big rechargeable battery that puts out heat.

This lozenge shaped device is not only a USB power bank that can keep your mobile devices topped up, but is also doubles as a miniature heater that ... until the 4,000 mAh battery runs down.

Rechargeable heated coffee mugs use a built-in battery to keep their contents warm. These batteries eventually run out and need to be topped off or recharged. The best mugs offer 1.5 to 3 hours of ...