Inventory Detector Block

[Conscript Gary]

So we've got the detector block, and it's awesome for automation.
We've also got the hopper, which is awesome for automation.
The hopper outputs a redstone signal when it's full, which allows us limitless reactions for the use of automation- things like diverting water flow to the next hopper, sending off storage minecarts, etc.
Now, this is all fine and excellent for the hopper, but what of other blocks that have inventories? Particularly the cauldron.

What I'm suggesting is some sort of alternate detector block, one that outputs a redstone signal whenever the container in front of it has a full inventory.

For some usage thoughts, go with the aforementioned cauldron. When it's full, you would get a redstone signal. You could use that to turn off your hibachis, slurp up the cauldron in a block dispenser to drop the cooked products, release some creative water flow to your storage solution and reset the whole merry process.
Storage minecarts could be routed along the same lengths of track if there was a way to differentiate between the full ones and the empty ones at junctions.
A pulley filled entirely with rope (or some sort of filler item like how you can gum hoppers up with clay), combined with a latch or something and a normal detector block at the bottom of the shaft could provide an elevator that constantly cycles up and down without obscene amounts of delayers and such.
A furnace could set off a lightblock when it's done smelting its stack.
And I'm sure a number of uses that haven't occurred to me.