Quote fromQuote fromPiston mod can propel items upwards, and a series of pistons with the right timing can raise them as high as you like. Triggering the pistons to start with might be difficult though, because a piston would destroy a pressure plate, and water couldn't run through one.
Thats what I was thinking. I just can't figure out a way to trigger it once an item lands on it.
Just rig up a clock and have it constantly pushing items into the air.