Also like ghosts, characters who are Astral Projecting may use Demonic Possession to take over host bodies, though this doesn't necessarily allow them to pry into their mind.
Now effectively a living ghost, the character can go just about anywhere, see and hear anything, and potentially engage in Invisible Jerkass behavior, depending on whether he can move objects telekinetically. Astral Projection is a magic/mystic practice which allows a character to detach either his soul or his conscious mind ( the distinction is important) from his body and let it wander freely, either invisibly in the material plane or out in the Spirit World.