When we're tired of uncomfortably stuffing toe warmers into our boots, we charge up the Hotronic XLP 2C BT Foot Warmer and take warmth to the next level. Three constant heat power settings and a fourth Power Boost setting can be easily selected via the battery pack's power button or a Bluetooth-enabled smartphone with the HOTRONIC Heat app. The app can also let us know the current battery level so we know when it's almost time to take them out of our boots for the next charge.