Wireless charging has come along in leaps and bounds over the past few years, but whilst the ability to power up a device from a short distance away is somewhat useful, it's still not convenient enough to convince most consumers that USB cables are redundant in this respect. Sure, wire-free charging seems an inevitable part of our digital future, but there's also a lingering feeling that there's much work to be done until it becomes a necessity, and several groups are looking to push the boundaries and bring these visions to reality. One system, which uses ultrasound to power devices that may, for example, be roaming on the other side of a room, is a prime example, and after years of development, looks a very exciting inroad.