This map shows that the desire and certain skills, in Minecraft PE you can even create giant robots capable to move and throw enemies with dynamite.
Take a block watcher, click it holding the active slots steel and flint, the piston is activated, the robot moves. To stop the easiest way is to break the piston or the blocks that it drives.
There is another clever way to stop that you could get yourself shot while driving (this action will break the engine).
Install Rise Of The Machines Map
- Download the map
- Remove the map from the archive
- Move the map by path: "/games/com.mojang/minecraftWorlds"
- Go in Minecraft PE > Play > Select the installed map
- Enjoy the game!