How do you connect a touchless button to a GPIO?

The Touchless buttons present a logic-level on/off signal at their output. Connecting them to a GPIO device is usually as simple is a connecting the button output to a GPIO input.

The buttons are 3.3/5V tolerant, so they interface readily with most devices.

In the case of our USB GPIO module, we can connect the button directly to GND/VCC and an input, and we can read the button output on our host machine.
Attached is a picture of a setup I use frequently on my desk.

How far can I use the touchless button?
That will depend greatly on the structure around the button. We typically get sensitivity at a range of 1/4" with the buttons as configured. The sensitivity is controlled by a fixed resistor on the board, however you can readily change the perceived sensitivity by the creative application of metal.

For instance, if I place my steel tweezers across the electrode, then I can activate the button by touching the tweezers, several inches from the button itself.
Pictures attached.