Also check out One-Way Dynamic Lighting. The name is misleading -- what it does is create a trigger area linked to a dynamic lighting line, so that when any token is put in the trigger area, the linked line goes away, allowing vision and movement, until the token leaves the trigger area again. It's available in the One-Click menu. The trigger area can be elsewhere on the map, any token can activated it, and all tokens with sight and movement are affected. Also look at Pathsplitter, which can be useful when someone blasts through a wall. Also on the One-Click.