These send hand or body position and movement information to the computer using sensors.
A more unusual idea is using plants and their natural sensors.
Other more complicated methods using multiple sensors is also possible.
It was the ideal way to find a target without using his own active sensors.
"I estimate three minutes before they can begin using their sensors," Daniels said.
It does this by using infrared sensors on the satellite.
Most of them use sensors and circuitry to monitor changes in a particular state.
Other systems that gather motion data usually use fewer sensors.
"It is not possible to obtain a positive identification using only ship's sensors."
If they thought to use their sensors, they could pick him out easily.