It's obviously a command block that's outputting the text, but the yogs don't stand on a pressure plate and it doesn't seem to be a tripwire or anything that activates the piston. I was told that it might be something to do with 'radius' or 'range' but I have no idea how to do it. Apparently to do that you don't need any redstone either.
Any help? Thank you.
---------- Post added 2012-11-22 at 10:33 PM ----------
'Lord Sargeras, sweep your molten fist through this world, so that it may be reborn in flames and darkness!'
'So the light's vaunted justice has finally arrived.'
'Boldly said. But I remain...unconvinced.' My Warrior
I assume you have read the Minecraft wiki?? It has information on radius, etc. I've not played with command blocks at all yet, but I assume you would use a combination of the @a (all players) and the r/rm commands (radius, minimum radius) on a redstone clock?