Now, battery-free gesture recognition technology

Scientists, including one of Indian-origin, have developed the first gesture recognition system that can be implemented for less than a dollar and does not require a battery.
University of Washington computer scientists built the low-cost gesture recognition system that runs without batteries and lets users control their electronic devices hidden from sight with simple hand movements.
The prototype, called "AllSee", uses existing TV signals as both a power source and the means for detecting a user's gesture command.
"This is the first gesture recognition system that can be implemented for less than a dollar and doesn't require a battery," said Shyam Gollakota, a UW assistant professor of computer science and engineering.

"You can leverage TV signals both as a source of power and as a source of gesture recognition," Gollakota said.
The researchers built a small sensor that can be placed on an electronic device such as a smartphone. The sensor uses an ultra-low-power receiver to extract and classify gesture information from wireless transmissions around us.

When a person gestures with the hand, it changes the amplitude of the wireless signals in the air. The AllSee sensors then recognise unique amplitude changes created by specific gestures.
Sensors use three to four times less power than existing gesture recognition systems by harvesting power from wireless transmissions. This allows for mobile devices to always have the gesture technology on and enabled.

Gesture recognition already is possible on some mobile devices but users have to first manually enable the feature and be able to see the device for the gesture technology to work, and if left on, the gesture system quickly drains the phone's battery.
In contrast, AllSee consumes only tens of microwatts of power and can always be left on. The user could gesture at the phone in a pocket or handbag to change the volume or mute the phone without having to touch or see the phone.
This technology could allow sensors to be attached to household electronics, making it possible to interact with everyday objects using gestures and also connect them to the Internet and to each other in an "Internet of Things" world.

The UW team tested AllSee's capabilities on smartphones and battery-free sensors using eight different hand gestures such as pushing or pulling to zoom in and out.
The prototype could correctly identify the gestures more than 90 per cent of the time while performed more than 2 feet away from the device.
Researchers have tested the technology for response time and whether it can distinguish between other motions and those directed at it.
They found that the technology's response time is less than 80 microseconds, which is 1,000 times faster than blinking an eye.