I don't see why they couldn't make one out of these retractable cords.
30' is way more than I need in the livingroom. If they scaled it down, I could see something like this working very well.
One thing to keep in mind is that the cable isn't as big of a deal as you think it will be. You're not going to be spinning around much (bad idea in general), and it's more natural than you think. Every use a corded drill or a vacuum cleaner? Now think about how much easier ti would be to use if the cord was always out of the way behind you by being attached to your back.
I had the same idea as you when the Vive was announced from what I've heard from developers and other first hand experiences it's not a good idea.
Here are some of the components I was considering: Extension Cord reel http://www.amazon.com/Bayco-SL-800-Professional-Retractable-30-Foot/dp/B000256R9G