Thats an interesting concept and design David.
At $219.00 though, mine is a really cheap hack!
I dont get cooled all over though, just the back area.
On seriously hot days I have sometimes just doused myself a bit with ice water from my pack because with my mesh jacket it pretty much dries out over a short period in any case.
Edit: Forgot to mention that before trying out the backprotector version i did try putting the bladder in my tank bag.
I didnt like the hose fuss much though..well i found it a fuss a little bit. Did like that it was completely off my back though.
I considered playing with a bumbag concept..because the bag is on the seat then, but attached to me.
But the backprotector design worked out so well for me that im staying with that.
I find it really comfortable.