I think you should be able to throw a snowball across a dark chasm to a button that triggers a piston bridge to protract out of the wall.
Players can take care of most of this machinery, but the bit that's missing is the button's functionality.
And if you're feeling especially generous, Mojang coder who is reading this forum post during your lunch hour: how about also making levers work this way too. Or for more obscure fun, have buttons activated only by snowballs, eggs, and arrows, while levers are activated by fishing lines.
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