Oh those industrial designers always seem to impress me... This time it's the portable beverage heater designed by Seungheon Lee. The molded plastic, single-use device is clipped to the side of a mug and creates heat via fuel cells. The long portion stays immersed in the liquid and thermographic ink changes the logo when the beverage is hot. It's just a concept design at the moment, but I can see something like this coming to market in the future.
Source: Yanko Design