Runeward tattoo

[Epsilon]

Just double checking on this item, because a DM I was playing with interpreted differently. (PFS Play)
I have all tattoos does this mean as long as a spells been caast withing 60 feet I know or do i still need to be spending an action using detect magic? Also do walls block range on it?

Runeward Tattoo (1000 gp, Magical Marketplace)
Each of these tattoos is keyed to a single school of magic. The bearer can use detect magic at will, but only to sense auras of that school. The bearer gains a +1 insight bonus on saving throws against spells and spell-like abilities of the keyed school and knows when such a spell or a spell-like ability has been cast withing 60 feet.

[dragonhunterq]

You know when a spell/SLA of the specific school has been cast within 60' automatically. but you won't know where or what spell/SLA without activating the tattoo's detect magic and concentrating in the right area.

I'd have the 60' sense blocked by the same things that block detect magic, but I could see others ruling differently. It doesn't actually give many clues as to how that works.

[Epsilon]

Just thinking, what if I fail a perception to notice, but an enemy in hiding cast a spell. Would I fail to act in a suprise round?

[Epsilon]

If it helps to figure out what blocks it, both Detect Magic and guidance are the spells used to craft it.