You can power almost anything by USB these days, so making a heating cap and neck warmer kit that can be connected to a USB battery and keep you warm for hours during cold days outside seems like an obvious idea. Amazingly, until the Real Heat Cap and Neck Warmer, apparently nobody had thought of it but now it's finally available, so the only thing let to do is pick your favorite color (there are four to choose from: dark gray, light gray, black, or beige) and you're good to go!
As soon as you plug the USB cable into your battery (not included), the Real Heat Cap and Neck Warmer starts heating up and in 60 seconds reaches full power. Use the remote control to choose which of the three modes you want (Quick Heat, Medium Warmth, Retain Warmth) and go out for a run, bike ride, or walk around town, all while well protected from the cold. Made of polyester and fleece, it is also effective against cold temperatures even without electricity!
The Real Heat Cap and Neck Warmer features: