Contingency
Evocation
Level: Sor/Wiz 6
Components: V, S, M, F
Casting Time: At least 10 minutes; see text
Range: Personal
Target: You
Duration: One day/level (D) or until discharged

You can place another spell upon your person so that it comes into effect under some condition you dictate when casting contingency. The contingency spell and the companion spell are cast at the same time. The 10-minute casting time is the minimum total for both castings; if the companion spell has a casting time longer than 10 minutes, use that instead.

The spell to be brought into effect by the contingency must be one that affects your person and be of a spell level no higher than one-third your caster level (rounded down, maximum 6th level).

The conditions needed to bring the spell into effect must be clear, although they can be general. In all cases, the contingency immediately brings into effect the companion spell, the latter being “cast” instantaneously when the prescribed circumstances occur. If complicated or convoluted conditions are prescribed, the whole spell combination (contingency and the companion magic) may fail when called on. The companion spell occurs based solely on the stated conditions, regardless of whether you want it to.

You can use only one contingency spell at a time; if a second is cast, the first one (if still active) is dispelled.

Material Component
That of the companion spell, plus quicksilver and an eyelash of an ogre mage, rakshasa, or similar spell-using creature.

Focus
A statuette of you carved from elephant ivory and decorated with gems (worth at least 1,500 gp). You must carry the focus for the contingency to work.

so, it casts a spell to distract them from the real spell like a trap or something, thus making them oblivious to the secondary part, until trigger say nightfall? but IC ?? sounds a bit too confusing to use out of a PnP game

Basically, you cast a spell and set a trigger, lets call it the word 'rainbow'. When someone says 'rainbow' the spell will immediately cast. Basically, you are casting a spell in safety so you don't have to when pressed in combat.

Baldur's Gate 2 had a cool implementation of it. But such a thing would be hard or impossible to implement in a game that wasn't designed to support it.

(You could do things like, "The spell triggers when I reach 25% health" or "The spell is immediately cast on the first enemy that comes into line-of-sight.)

Well, it should be cool if everyone involved/affected agrees. Depends on what you do with it, but I think common sense goes a long way.

It's a classic thing. No great mage is in danger of dying at swordpoint, because they always have contingencies in place to whisk them away and whatnot. Doesn't particularly make for balanced PCs, but it's good for reminding PCs that attacking Maaril the Dragonmage wasn't the smartest of pastimes to do in Waterdeep, for example.

It is, however, possible to request custom scripted items that fire several pre-determined spell effects simultaneously, simulating a sequencer. Whether it's approved, of course, depends on the power of the item.

Every spellcaster can take the feat Quicken Spell, and Auto Quicken 1,2,3 at epic levels with the right builds. That's probably the closest you can get to Contingency.

That's not contingency, that's just Mirror Image + Teleport.

Who needs contingency? Timestop, Improved Alacrity, Magic Missile x 9 (since BG had 0 casting time for them, and Imp Alacrity makes it 0 time between spells).

Of course, I once tried that on someone who had spellturning pop up. Not pleasant.
Anyway, I must get one of those widgets.