Is it possible to construct something that will run automatically whenever a player is nearby, say within a chunk's range, without that player having to trigger something like a pressure pad or detector rail ?

What I'm trying to do is get some pistons to move in this situation, so for example if someone was walking along something might light up on a distant hill

The only way I can think of doing this is to have a cavern underground with a load of pressure plates wired up to pistons on the surface, and an army of snow golems down there to wander around and hit the pressure plates. But they don't seem to spawn until you're pretty near.