Arcane sight would be just like the spell of the same name, but always active.
Found on a previous conversion thread...
Dweomersight (Su): A balhannoth can sense the presence and position of magic auras within 120 feet of itself, and knows the strength and school of each one. It can pinpoint the location of any creature with ongoing spells cast on it, carrying magic items, or otherwise using magic, and it can notice anything within the area of a magic effect (including its own dimensional lock aura). This otherwise functions like blindsense.