We've played a variation of this in 8-ball at the club where I play most. At first the better guys were using it as a way of handicapping themselves when playing me. (When I was brand-new to the game, and really green.) I quickly decided I wanted to play that way as well; it really is fun, and makes you think.
Basically, our game is regular called-shot 8-ball. Before you shoot you have to call the next ball and pocket you will shoot after the ball you are on currently. If you miss, you reset your calls when you get back to the table, except for shooting on the 8. You still have to put the 8 in the pocket you called the first time you shot at it.
I imagine it would work much the same way and be as much fun in 9-ball, too.
Just a way to mix things up some. We haven't played that in a while, I think I might suggest it tonite if I get over there.