http://lancasteronline.com/article/local/861483_Magical-NeverWet-arrives-in-stores.html
I've seen this pop up a time or two on Facebook and io9 just ran a story on it.  It's being sold by Rust-Oleum at Home Depot and goes for about $20 a can.
The video (in the article above) is pretty impressive, and I've seen some youtube reviews that show it actually works.  The only drawback I've seen has been some clouding (milky looking streaks) caused by the spray but that's common for most clearcoats I've used and may be user error.

Has anyone tried it?  I'd assume it would take a few cans to cover a full scale Tardis, but it would be worth it to me.  I hate having it in a hundred pieces in my shed 360 days a year.

One of the videos I watched said it dries "milky" so that seems to be the expected result and it might not look good on a Tardis.  That said, it's pretty amazing stuff.

-Joe

Would weathering take care of those "milky" patches? Or is this NeverWet intended to be the final coat, to seal in the weathering effects?

Dino.

Given it's properties I doubt you could put any other finishes on top of it.

Looks very interesting but I would imagine the coverage for the cans would not be great ("says" each 2 can pack covers 10 - 15 sq ft) and at $19.97 it would make for an expensive coating.   Though having watched the video I kind of do want to try some on silly things just to see

I'd say it would be roughly a $200 investment.

From the videos I've seen, the milky residue may be caused by people who aren't really experienced with using spray paint or clearcoat.  It may be where they've held the can too close, didn't shake it property before application or other common problems. 
I'm still not 100% sure on that, though.  I imagine you can sand off the milky spots after it's dried and add a little more paint then try to spray it again.  I doubt it would take paint after you've applied the NeverWet so it likely can't be used to treat the wood prior to painting.

This wouldn't be used to seal the Tardis off so rain doesn't get inside or something, but it might seal the wood itself so it wouldn't absorb moisture and warp or decay.  I haven't seen how it holds up to changes in temperature or weather in general (maybe it will come off after a few heavy rains?  Crack, flake or melt in the heat?).  I haven't seen how it affects the color either, as most clear sprays will make the base color a shade or two darker.

I built my Tardis to be used at conventions but it's in about 35 pieces, taking up 50% of my shed and I really kinda want to look at it more than a few times a year.  I might give this a shot sometime soon just so I can have it up outside in the summer and fall.

http://www.youtube.com/watch?v=BmMGv8A4QvE

At about 1:38 in the linked video they state "never wet dries to a milky haze and may there for may change the appearance or color of some material".  So I would assume that is the expected result.  The only question would be how milky.

Wanted to pass on a little more info on this.
The original demo reel shows them applying it to things like smartphones or things with color and there's no visible haze (it's implied it's on the smart phone because of the way the water beads and rolls off of the screen).  Even the recent video posted in the thread says it may dry with a sort of milky haze.
However the box has a warning that things will dry with a frosted white finish.  I've seen some demos of this (one from Wired, I think) that shows it dries REALLY white and will definitely change the color of whatever you put it on.
On top of this, I've heard of this stuff quickly washing away or being easily wiped off with your fingers even after it has had a long time to dry.

As of now this really cannot be recommended for a Tardis exterior.  It may be usable for your interior or for the windows if you feel it necessary.  I'm sure thy will eventually release a clear version or some extra strength formula or something but for now, I wouldn't recommend it.

Well... a little more information here... just watched a video on youtube not remotely related to tardises or prop building, i have to note and heard 4 crucial words that would make me not use this on a tardis

Neverwet degrades in sunlight

I am really glad I read this thread. I was watching the amazing videos of Ultra Ever Dry and Never Wet and was thinking (like you) how wonderful it would be to use as a TARDIS weatherproofing treatment .

Less expensive alternative here:

DIY Hydrophobic Coating [Never Wet, Ultra Ever Dry Replacement]
https://www.youtube.com/watch?v=OzN8uI5USXM

DIY Never Wet water repellent SURVIVALIST STYLE
https://www.youtube.com/watch?v=ujEWwUMC5Y4&feature=youtu.be

Krylon Color Master Cover max Clear Coat and Arred XX Ultra Fresh antiperspirant. Spray the Clear Coat first then while the clear coat is still wet apply the antiperspirant. Let dry 1 hour.

Cyclopentasiloxane is the component of the antiperspirant that functions as the hydrophobic element to this project. While not quite as hydrophobic the commercial coatings like Never Wet and Ultra Ever Dry, it is significantly less expensive and functions well enough for nearly all the same purposes.

*Neverwet lasts 25% longer than this less expensive solution.

(apparently there is a limit to how long an application will last - probably due to UV exposure .... now if someone would just tell me how long an application will last. )