I want to subscribe to a callback method for when the sleep timeout occurs, not the commands that the sleep timeout event issues.  Something like:

	Slim::Control::Request::subscribe(\&commandCallbackSleep, [['sleeptime']]);

However, there doesn't appear to be such a command to subscribe to.

Could the helper function _sleepPowerOff issue an executeRequest for a new command (eg. 'sleeptime')?  Perhaps move the stop and power commands into the 'sleeptime' command.

Then plugins could subscribe to the callback method to perform other tasks, such as suspending the server.