Why is it an app?
When we do cmd+tab, why does amphetamine even come up? Why can't it just live in the taskbar as a service?
In Amphetamine’s Preferences, on the General tab, simply uncheck the checkbox that says “Show Amphetamine’s icon in the Dock.” This is turned on by default because Apple requires it. Apple has rejected Amphetamine from the App Store with the Dock icon hidden by default.
Charles Magnuson commented
This feature already exists in Amphetamine: http://ca.mag.cm/2p0W3G1Y2J2J