The current prototype is based on an Adafruit Feather 32u4 board which has the Atmel ATmega32u4 micro. I've soldered pins A0 and GND to that board and used the internal pull-up resistor of the ATmega32u4 on pin A0. When you hit the button, a sequence of keystrokes is sent over a USB HID interface to the computer. The keystrokes depend on the operating system so when I compile the firmware, it's OS dependent.
The article addresses a very common problem. Drills are not the best example of tools to rent, since they relatively cheap and you use them quite often. I personally have gone through this thought process every time I worked on my car and needed new expensive tools that are used once. When I moved to a house, I always needed equipment (not only tools) on a short term basis. This is why I started https://www.1000tools.com I wanted to be able to rent tools [specifically tools] from people around me and couldn't find a good enough solution. So, we built our solution.
It's live and open in select cities, 8 weeks old startup.