It's -2 if you turn the wireless on though! So you're half right!
Core p431
Concealable holster: This small holster can be worn
on the ankle, clipped to the forearm, in the small of the
back, or anywhere else it’s unlikely to be seen. The concealable
holster adds –1 to the item’s Concealability (p.
419). Only pistols and tasers fit in a Concealable Holster.
Wireless: Wireless sensors and a smart-fabric coated
weave allow the holster to alter color and texture in real
time adding an additional –1 to the item’s Concealability.
Ahh, fair enough...but now you have to worry about people finding your holster in the matrix. Since that's a matrix perception test, I assume any commlink can do it, right? If not, then at least you only have to worry about people rich enough to pack decks, but otherwise, it seems like it would be easier to spot your gun with a computer than with eyes. Never got my head around the matrix enough to know if this is true, so I'm just talking out of my ass.