I have a laser cutter kit, which came with a controller that worked (!) using an android app, SCARVE. That piece of junk went in the bin

My idea is to do similar with a Cronos CNC/Laser GRBL controller (Arduino based) and offline board. I have a couple of spare Toshiba Flashair WIFI SD cards (I use one in my 3D printer), so one will be assigned to the offline controller. It is an easy way to get Gcode to the machine to run it offline.

I found that when the offline controller is connected to the board, LaserGRBL would not do certain functions, such as upload GRBL parameters to the board or jog the machine directly. To that end I plan a similar multi pole switch to disconnect TX, RX and 5V.