Dungeons & Dragons 3.5 Feat: Persistent Spell

You can make a spell last all day.

Extend Spell (PH)

Spells with a fixed or personal range can have their duration increased to 24 hours. Spells of instantaneous duration cannot be affected by this feat, nor can spells whose effects are discharged. You don't need to maintain concentration on persistent detect spells (such as detect magic or detect thoughts) for you to be aware of the mere presence or absence of the subject detected, but gaining additional information requires concentration as normal. A persistent spell uses up a spell slot six levels higher than the spell's actual level.
( Complete Arcane, p. 81)