I bought Supreme Slate of the Mind over a year ago from Tannen's Magic Shop (http://www.tannens.com) in New York. It was a nice place to visit, friendly staff and fun tricks.
The Supreme Slate of the Mind is a whiteboard, divided to 6 windows. You show all windows empty. Then you ask one of the audience to pick for example a colour, think about it, repeat the colour again and again in his mind, and of course visualize it. You stare at the person's eyes and then you turn the slate to you and write something in one of the windows and cover it with a magnetic lid. Then the person reveals for the audience what color he was thinking of and you write it in the window above the closed frame you just covered.
The same is repeated, now with any number between 0 and 9999. You write in a window and cover it. Same goes for the 3rd frame, for example a city, anywhere in the world.
Now you have 3 covered windows and 3 open windows, where you have written what the spectators were thinking about.
You then remove the lids, one by one, reveiling that you had read their minds, as you wrote in the bottom row what they were thinking off and covered them, before they revealed their thoughts to the rest of the audience.
The methode is clever, the slate is well made and the effect is good!
You can even write with 2 different colours (up and down) and the writing is not identical, so there is no carbon copy involved.
The downside is that the slate is rather heavy to hold for a long time and to travel with and it costs 250$, which is expensive, but of course you have an excellent mind reading trick in your routine.
Difficulty in performing would be 2.
I would rate it 9/10
