A survey developed by the Ph.D. candidate Yu-Chih Tung of the University of Michigan is to add pressure recognition to smartphones without the need for specific hardware for this.
In addition to the touch pressure, as in the 3D Touch available on iPhone 6S, the new software allows you to recognize when the device is being tightened. Called ForcePhone, the software does not require additional hardware to work, only the speaker and microphone already available on the devices.

[youtube https://www.youtube.com/watch?v=HioOiMzxBM&w=560&h=315]

The operation is simple and genius, causing the smartphone to emit a constant sound signal of 18 kHz, imperceptible to the human ear, but detectable by the microphone of the device. By pressing the screen or tightening the device, the change of the signal is detected by the microphone, transforming the variation into commands in the system, such as unlocking the screen or making an emergency call just by tightening the sides of the device.
The novelty will be presented in MobiSys 2016In Singapore.
via TheNextWeb