I want to pass objects through each other AND detect the collision

I'm trying to work out what combination of rigid bodies, isKinematic and isTrigger need to be in place such that i can have two objects pass through eachother without effecting eachother physically, but still fire a collision (in either onTriggerEnter or onCollisionEnter.

Let me go into more detail:

The game i'm working on contains "ghost" objects, the players hand can pass through them (but i need to know when this happens so i can apply some chilling effects etc) but the ghost objects must still collide and interact with eachother (so I cannot temporarily make the object being touched kinematic for example).

Any helpful hints or ideas? I'm new to unity (if you haven't guessed already)