OK, let's walk through the false positives issue a minute. There are two critical points that must be kept in mind.
1) the moss in the tip has different characteristics from moss in the wild (or on a wall). The most significant is range. The tip or badge or whatever has a range of 10 cm. 4 (well, 3.9) inches. Not from the wearer, from the device itself. (For convenience let's make it a badge.) The moss in the wild has a range of up to 60 meters. (10 x Force). The glowand, as described in AR 65, doesn't have as many false positives for the simple fact of range.
2) Neither the wand nor the wild moss have false positives. The misuse of this term is leading to confusion, so let's correct it. A false positive is "it signals but there is nothing there." What the moss signals is that there is SOMETHING there. It may not be a cast spell; instead it may be a change in background or an astral walker passing through it. All those are something that security needs to know.
a) Change in background - is it artificial in an attempt to hide an infiltration attempt? Is it "natural" and the prelude to a major geological or astral event (earthquake? ghostrising?) Security wants to know.
b) astral entity. We think we have the only astral entities here. If there are more we'd kinda like to know. If our astral patrol doesn't mention the entity we REALLY want to know.
c) spell. Obvious, yet apparently the obvious is being missed. The only spells that will trigger an alert are those that are cast or have an effect within 4 inches of the badge. Joe Wyldmage in the lab is tossing fireballs left and right? No hits on the meter. First because of range, and second because there are (I hope) wards between the lab and outside.
Now all those said, it's possible there are 'local artifacts' - local peculiarities that cause the signal to go off. Maybe there's a ley line through the property. Maybe there's an ancient spirit and part of its walk of shame goes right through the donut cabinet three times a week. Security system pros deal with those a lot. The fix is pretty old, too. For the first week a tech - or for this a mage - is on duty 24/7 and checks out every single alert. He notes time and location, and the events get logged and mapped. If necessary this goes for a month, but that's rare.
Bottom line, after a month it's a system. Your spirits' patrols are known, both timing and route, and can be matched if/when signals occur. There's a wobble at 2348 Friday night? Yep, Old Horace right on schedule (and he better leave the sprinkles on the chocolate this time.)
If something new happens and it starts looking erratic, the security techs get called. They look to see if something new has been added. But what everyone figures is really happening is someone's screwing with the system. Why?
Because the moss doesn't go off for no reason.
I wouldn't use the system everywhere. Definitely not in magic research labs. But in the corporate HQs? In the weapons research labs and the nano labs and the...? If it's not using magic, or if the magic to be used is controlled and contained, heck yes. I'm using very precise Force 1 spells on "this", and suddenly the badge of the observer 5 meters away goes off. It ain't my spell, and it means there is a problem.
4 inch sensitive range. It's going off if someone walks through it, if background changes, or the wearer is the caster or target of a spell. Ain't none of that stuff to be ignored.