I couldn't be bothered typing so this is a cut and paste from another's comment, which sums it up.
This falls squarely into the "Good in theory, fail in practise" category, Sitting right beside the bush winch.
Actually the more I think about it, I don't even think its that great in theory, its an even bigger fail than the bush winch.
Lets say we're bogged(really bogged, not just sunk in the sand where 2 minutes with a shovel would see you simply drive out as in their video).
First up, we need an anchor point, make that 2 anchor points, each one lined up nicely with a wheel. How likely is that ever to happen ?
(And yes we will need 2, because we are really bogged and if we pull from one side of the vehicle only, we start to turn sideways and the ropes will jump off)
Ok, so the stars have aligned and we have our anchor points, lets start winching.
Scenario 1, We have an open diff, one wheel spun, the other didn't, it pulled us out of line with the anchor points and the ropes jumped off. So now I have one set of ropes tangled around my diff, time have to crawl under and untangle it. Bugger !!
Scenario 2, we have a LSD/locked diff, both sides pull evenly, and then the front catches in a rut, turns us out of alignment and the ropes jump off..... Bugger !!
Scenario 3, the stars have stayed aligned and we're out !! Hooray, lets grab the jack and jack each side up and pull the ropes off....... hmmm hang on, if we have to jack it anyway, why didn't we just jack it and pack under the tyres and drive out in the first place ???
There may well be a rare occasion where this system might work, But, you would be far better off to carry a good long handled shovel and a decent jack(and jacking plate). A bit of shovelling or jack n pack(or both) will see you on your way most times.