Taking off mask at night

I'm feeling crappy today because I woke to find I had not been wearing my mask for two hours. I had turned off the machine without any memory of doing so.

Is there any kind of alarm that might wake me if I do this? I'm sure I start snoring if I take the mask off, so I figure some device that sounds an alarm if it detects snoring would work. Another idea would be an alarm that goes into the power line of the machine. It would go off if it detected a major drop in power consumption.

Any ideas?