Is instant summons, well, instant? The spell says that you need to speak a single word to summon an item to your hand. Does that mean it's a free action like talking or a standard action like word activated magical item?
The spell lists it as a standard action.
Casting it on an item is, but what sort of action is it to retrieve the item?
Thereafter, you can summon the item by speaking a special word (set by you when the spell is cast) and crushing the gem. The item appears instantly in your hand.
Not sure if you could crush the gem as a free action. The spell should list the action, but I would assume the default of a standard action. Expect heavy table variation.