This is a mockup of a everything-agnostic helper
That is supposed to be called from a ACPI event listener
(or an X-independent key handler) to determine the active session
and react to certain user-related events
(like brightness up/down, speaker mute/unmute, etc.)

What this does, it does stably.
TODO:
 * Support different init systems
 * Support running both in user session and as a system service.