"What is a PipBuck? A PipBuck is a device, worn on a foreleg just above the hoof, issued to every pony in a Stable when they become old enough to start work. A blending of unicorn pony magic and science, your PipBuck will keep a constant measure of your health and even help administer healing poultices and other medicine, track and organize everything in your saddlepacks, assist in repairs, and keep all manner of notes and maps available at a hooftap. Plus, it allows you to listen to the Stable broadcast whenever you would like as it can tune into and decrypt just about any radio frequency. And that’s not all. A pony’s PipBuck generates an E.F.S. (Eyes-Forward Sparkle) that will indicate direction and help gauge whether the ponies or creatures around you are hostile.
And, perhaps most impressively, a PipBuck can magically aid you in a fight for brief periods of time through use of the S.A.T.S. (Stable-Tec Arcane Targeting Spell). Oh, and a feature not to be forgotten: it can keep track of the location of tagged objects or people, including the wearers of other PipBucks. So if a pony somehow got lost -- don’t ask me how you could get lost in a Stable, but it does happen on occasion -- then anypony who knew the lost pony’s tag could find them instantly. It can even be made to glow like a lamp."
While many functions on the PipBuck are passive free actions. Some, like the S.A.T.S costs AP to use. Others can be activated through AP, or through willpower, depending on your model.