The Reon Pocket Pro Plus is the most futuristic product I’ve tested yet (still waiting for that flying car). It’s essentially a personal air conditioning system that uses sensors, or your manual inputs, to regulate your body temperature. When worn, it sits at the top of your back and uses a stainless steel plate that warms and cools.
It has effective heating and cooling capabilities that are personally adjustable to you via an easy-to-use smartphone app, or with the on-board buttons — but these are a little hard to reach if you’re wearing the device on your back.