The Epiphany One Puck hides a small stirling engine inside the coaster that turns heat disparities into usable energy. It doesn’t work with all drinks – tap water right out of the faucet, for instance, isn’t likely to help your cause. Instead, the generator works best with either very hot drinks or very cold drinks, since they create the highest amount of heat disparity. Plenty useful when you’re down to a bar and dwindling fast. Let’s hope it won’t explode… and you won’t get arrested on terror… “charges”.