In Cura there is a post-processing script, Pause at Height, that will insert gcode to pause the printer and wait for the user to continue and the current implementation uses M0.
According to the RepRap Wiki, M0 turns off heaters and motors. I'd like a command that waits for the user to continue but doesn't turn off heaters and motors. Would it be possible to add optional parameter(s) to M0 that would control this behavior?