Desktop CNC machines are cheaply available these days and commonly use GRBL controller boards. However, they usually lack some of the luxuries afforded by their bigger, much more expensive, cousins. One of the main items I felt my cheap Chinese 1610 CNC lacked was a pendant: a handheld controller connected to the machine via a cable.
So, as there didn't seem to be much in the way of open-source GRBL pendants available, I decided to design my own using a 3D printed case, an ESP32 microcontroller and some electronics components. It requires a fair bit of soldering, but that's well worth the effort to be able to move the cutting head (jog mode), set the cutter origin (zeroing mode) and turn a LASER on or off (focussing mode).
It also has a pass-through Bluetooth mode that lets you connect your machine wirelessly to your CNC software on a PC or tablet/smartphone. I find it invaluable for setting up my CNC machine and wirelessly cutting and if you'd like to make one too you can find the build details and firmware source code, all open-source, at the link below: