This was my response as well. The problem doesn't make much sense. Personally I would have made the "mood detector" start button show a progress bar on the UI so that it is obvious that it is doing something, and how long it will take to start the "mood detector". This internal "queue" and "counter" stuff is ridiculous. Just let users press the button, show them a progress indicator and don't let them press the button until the state is changed to fully on/off.
When it comes to third party apps and other things turning the mood detector on and off without the users permission or notification that makes no sense and sounds like a bad idea in the first place. But if it is essential I would make it pop up a confirmation request on the UI so that the user can not only choose whether or not to allow the on/off behavior, but so they will also be aware that the device is going to be turning on or off. Once again while the device is turning on or off show the progress bar.
Perhaps the "mood detector" isn't the most intuitive example. But imagine it's some sort of computer peripheral that several applications make use of. The problem seems simple until multiple agents start to mess with it. So you start out with steve's simple model, and you too will progress to what he ended up with eventually.
on/off seems easy, but it's hard in complex systems. Like how complex can it be to turn windows vista on and off, right?
When it comes to third party apps and other things turning the mood detector on and off without the users permission or notification that makes no sense and sounds like a bad idea in the first place. But if it is essential I would make it pop up a confirmation request on the UI so that the user can not only choose whether or not to allow the on/off behavior, but so they will also be aware that the device is going to be turning on or off. Once again while the device is turning on or off show the progress bar.