Block update detection is a very little known feature of redstone, partly because it hardly uses redstone and partly because it requires a very non-intuitive 'engine' to use it. It's almost an entirely different field to normal redstone, which deals with power, because it's a physical technology. It requires a physical input and you will only get a physical output.
By this I mean that, once you've created the engine, any kind of block update next to the master piston will activate it. This "block update" can be adding a block, removing a block, liquids running into the block, a block updating itself (for example an off furnace turning into and on furnace when it starts to cook something or vice versa) and, importantly, when another piston updates the block next to the master piston.
This means that you can build a chain of block update detectors which all update the next one. I'm currently pioneering the research into exactly what can be done with this technology (Wow, that sounded extremely pretentious) in terms of different inputs and outputs.
In this project I'll be updating my downloadable file with new SCHEMATIC files for MCEdit, but if anyone has a computer which isn't able to run MCEdit, or even just doesn't like using it, then just ask and I'll add a save file of the world I've been building my redstone contraptions in.