Divination seems to be all about bonus features since its only spell is pretty meh. Here is a suggestion:
Epic Focus Divination: -sentry creates a stealthed/invisible inanimate object where the caster is standing, it will warn the caster telepathically of any individual who pass through with a message: "Someone is in the vicinity, they look [uses mage's spot skills to point out their appearance akin to -investigate]. " Lasts 1 turn/level.
The sentry's spot is based on the caster's spot, listen doesn't carries through, and it doesn't has see invisibility/true seeing(nor can it be cast on them). It can be killed/destroyed if it's seen, it warns the mage if destroyed.
