If you connect GRBL using a network (WiFi) to serial converter, you then can connect as many GCode senders as you want all communicating to the same network address (GRBL controller). You then can use a simple ESP8266 processor to do send the jog commands independant of the GCode sender. I have connected my GRBL controllers using WiFi and have plans for next year to make a (simple) pendant for GRBL.