I believe it is using your mind and concentrating within to see into the future.
There is scientific evidence to support that blocking all outwards senses opens up a 6th sense or exposes it on a more physical level.

There is a standard technique used too by scientists, that involves puting some ear phones that make a certain sound to balance out brain waves and closing your eyes. Not really sure about how they do it to be honest but something a long those lines.
What I ment to say was I didn't know much about Buddhist monks doing this
But I suppose this is the orignal question of scaredstar's post.