Allow stuff to happen only if the target is above or below a certain health threshold when the drop is triggered (for use with right/left click, or hit)

probably easiest to implement by integer health remaining, but percentages would be neat too

...percentages would be no more difficult than integer health.

Side note... don't do integer health. Do number of hearts. I think that has less potential for confusion.

(This means that numbers like 1.5 are valid values, of course.)