A removable under blanket that could be taken off a canvas rug to wash when muddy and hairy!

A cell phone holder, on the saddle

I need a bubble wrap suit for my horse! He always seems to hurt himself! :)

And Christine, you really want the cell phone holder on yourself, that way if you come off, you can call for help...as 2 of my friends found out last week when they both got thrown on a trail ride. No phone = hobbling home for help!

Fly spray that actually works and doesn't leave an oily, gross residue.
A cure for ringbone and navicular, that doesn't include surgery.
A machine that would actually let you hear what your horse was thinking(though I think it might be scary)