I bought an arcade controller kit from Aliexpress and I didn't like the usb controller board in the kit. I also wanted to make it wireless so I've made bluetooth version of it. Basically it's just a hardware debouncing board for cheap nrf51822 modules.
The goal here is to build a bluetooth controller with really low latency. It should be around 6ms now but I will work more on the firmware. I've temporarily put it in a cardboard box but I'm thinking about making a wooden box for it. And I will also add 18650 battery and charging circuit for it.
Firmware uses HIDoverGATT so you don't need any driver on most devices. Of course I could've just bought a bluetooth controller and solder the buttons to it but where is the fun in that.
I've used mbed platform since it supports nrf51822 and I've designed the PCB in Circuit Maker.