Scrying

Scrying is the magical ability to use one's senses to experience events far away.

Magical sensor
Many divination spells of the scrying subschool create a magical sensor that sends the caster information. The sensor has the sensory acuity of the caster and acts though it were a separate, independent organ. Any intelligent creature can notice an active magical sensor. The sensor can be dispelled.

Limits
Scrying cannot penetrate lead. Several magic spells, antimagic field, mind blank, nondetection and wardmist can block scrying. Magical items such as weirdstones can block scrying. The semi-precious stone tchazar could blur the scrying of anything close to it.