To reduce the number of accidentally destroyed items I built a Flushable Garbage Disposal. Just put your junk items into the barrel, check that there aren't any valuables in the mix, and press the flush button.
If you put items into the barrel and then remove ALL of them before flushing, the disposal has to be reset (indicated by the redstone lamp turning off) before the next usage by pressing the flush button once.
It's not the most compact redstone circuitry but it's small enough so that the only visible part is the barrel (and the redstone lamp) when built behind a wall.
Feel free to download and use this build however you like, but please give credit if you do :)