This is the case for a very simple 2 Button Clicker I created for Presentations. The Code can be found here on my github page: https://github.com/Neokil/simple-clicker

To make it work simply get a Micro-Controller of your choice that fits into the 23mm by 35mm, I used a Pro-Micro for that. Wire up some switches to the pins 3 and 4, upload the firmware and thats it.