Capacitive touch sensors are entirely in the domain of DIY, requiring little more than a carefully-chosen conductive surface ...

The sensor forms an image and OpenCV detects the actual touch configuration. It appears you can use the raw data from the Arduino, too, but it might be a little harder.

Kano’s Motion Sensor Kit is a USB-pluggable sensor that detects direction and distance with infrared. You hook it up to Kano Code to make interactive games, musical instruments, or whatever else ...

This example code wakes the onboard indicator (LED at D13) of the Arduino when a tilt is inputted by the tilt sensor module through the occupied digital input (D2).