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.
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.
Other more complicated methods using multiple sensors is also possible.
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.
A detailed description of the sensors and measurements used in the study can be seen below.
"It is not possible to obtain a positive identification using only ship's sensors."