I give all credit to Iredstone for apple and android. How it works is that when you turn it on and shoot a arrow out a dispenser it signals a piston to stop moving. With no mods.
YOU HAVE TO SEE IT TO BELVIEVE IT! The world download is the schematic.

How to reset it:

First you break the redstone by the repeater shutting off 2 pistons.

Second put the wool and iron bar back on the pistons.

Next you collect the arrows.

Finally you break the boat and replace it.