Wearables face a vexing paradox. We want them to get smaller and smaller, yet smaller devices have less room available for buttons, touch pads, and other methods of controlling them. Solutions that work great for a desktop computer or tablet do not necessarily work for wearables.

Researchers at the Carnegie Mellon Electrical and Computer Engineering Department have come up with a low-cost way to control small devices. They have harnessed electrical fields, the invisible energy “auras” that can surround a device. (Think of how a Theremin works, for example.) Their AuraSense technology relies on tiny antennas in a device to  project a field. Bringing a finger into range causes a disruption of the field that can be detected. By analyzing the disruptions — and how they change over time — the system can detect discrete actions and motions that can be translated into control commands for the device.

Using an off-the-shelf smartwatch, the researchers were able to add electric field sensing at a cost of about $5. The technology is fast — about 200 frames per second — and can even work through clothing. The team tested a number of different transmitting and receiving antenna configurations. They found that the system could even detect “one-handed” inputs, where simply changing the position of the hand wearing the watch could signal a command.

For those of us who don’t want to wear a smartwatch the size of a hockey puck, this is an exciting development. It also shows that we may be able to build non-touch controls into other wearable devices, allowing users to issue commands discretely that won’t be disruptive or noticed by others.