Eyes to the sky
( Unearthed Arcana, p. 93)[Spelltouched]
You have an instinctive sense of when someone is magically watching you.
Prerequisite
Exposure to scrying or greater scrying spell,
Benefit
You automatically spot the magical sensor created by a spell of the scrying subtype (arcane eye, clairaudience/clairvoyance, greater scrying, or scrying) if it's within 40 feet of you.