NEC innovated the first liquid cooler for smartphone SoCs, with its new Medias X. The cooler uses a small coolant channel that activates when the SoC is too hot, circulating heat from the chip to a graphite dissipation plate, from where it's passively vented out. The solution may seem complex compared to a heatsink, but ends up being lighter, which goes a long way in smartphones, considering the Galaxy S 4, for example, weighs no more than 130 g.
Interestingly, the chip NEC is cooling on the Medias X isn't particularly known to be hot, the Snapdragon 600, the same chip that drives the HTC One and some batches of the Galaxy S 4. Other specs on the Medias X include a 4.7-inch 720p screen, a 13.1-megapixel Sony Exmor sensor camera, and the latest Android 4.2 "Jelly Bean."