This mod has one purpose: save your life when you are falling to death. You've probably seen videos of people quickly placing water or slime under them to keep from dying; this mod removes the skill involved in that.
If you have accumulated enough fall damage (taking into account feather falling, protection, slow falling, and jump boost) to lose at least 95% of your current health, the mod will make the player look straight down, will scan their hotbar for (in order of use): water bucket, totem of undying, ender pearl, slime, cobweb, hay bale, or bed. It will then select the highest priority one, and then spam right-click to try and place that item beneath the player to save their life - be that with all their health or half a heart.
Hold down the Vertigo key (default V) while falling to try and have your life saved.
Will not work with items, effects, or enchantments that are not listed above.
Will not work if you do not hold down the vertigo key when falling.
Will not work if you aren't going to lose 95% or more of your current HP.
Is not aware of any items outside of the hotbar, and will not move them to your hotbar for you.
Enderpearls are a mixed bag; use at your own risk.
Works on vanilla servers - but don't exploit it. Ask the server admins if it is ok: if they say no, don't use it.