Camping World has one system... although labeled for front jacks, the info states that it can also be used for the slide-out. Note that it's only for a 30 amp service.
http://www.campingworld.com/shopping...l-system/37668
I found nothing else relevant to retail purchases. You might try contacting a Keystone dealer who sells travel trailers that have 'remote' systems as a standard item. Cougar, for one... any others? Dealer should be able to tell you if those systems can be added.
Hope this helps,
Terri, the Chevy co-pilot