• mix of automatic precision dropper and dispenser
• fires only if items inside
• delay of at least n {ticks} (1s) between each
• recipe: "automatic precision dropper" + bow + ...

usage:

• throwing of chicken/hatchery-eggs

This is really hard to do by the way that the Dispenser code works (or used to work, as I attempted this in the past). I still like the idea though, so keeping it open.

alternative:

• is there a block (or could you add one) which fires a redstone signal
  to the block in front as long it detects an item in its inventory
  (combination of redstone clock, comparator and so on)