Triggering external program upon g code command

Hello,

If this is in the wrong forum, please let me know which is correct. This is my first post-- yay!-- on linuxcnc

I'd like to kick off an external program when I encounter a tool change code in LinuxCNC. Is it possible to do this? If so, where can I look for the documentation and/or examples?

Here's why I'd like to do this:

My CNC is setup in the garage, and it's a bit of a PITA to go check on it constantly. I don't have the machine networked into my wifi or wired networks, and I'd like to keep it that way. So, I'm going to take a couple of Arduinos with XBee radio transmitters. One setup will be hooked up to the CNC, the other to a "remote" I keep around the house. When the gcode tool change command is reached, it will trigger a program, which will use the setup to send a signal to my "remote", which will ding, light up, or shock me to let me know I need to waddle down to the machine and change its tool

Thanks!

Max

Here's the necessary G-code reference: I didn't use any.

I rigged up a cheapo webcam so I could look in on mine down in the basement. (I happened to have run network down, but I could have used a wireless adapter too.)

After much tweaking, I found out that I still have to phone home to get someone to go back down there and turn the light back on, and then they might as well just look at the machine and tell me how far it's gotten...

I realize LinuxCNC is a real time OS (RTOS), but couldn't running a program such as VNC cause problems with the milling job? If the process running it has issues, is it possible that the LinuxCNC stepper controllers might get pre-empted in the scheduler, causing the motors to behave incorrectly?

Or, can we run a billion other processes and still be fine simply because it is a RTOS?