Well, the rules say that you can talk even when it´s not your turn, so you could trigger Contingency to a certain word and make a virtual immediate spell (it´s even better than immediate, since it´s a free action).
The downside is that you must decide all th details of the contingencied spell when you cast Contingency, so, for example, you wouldn´t want to trigger Fireball to it, since you can´t really aim the spell. It works better with spell you´d cast on yourself.