Apparently, with the latest update, the BOSS GT-100 allows users to output midi signals from a normal guitar 1/4" output.
http://www.bossus.com/gear/productdetails.php?ProductId=1187
Not sure how effectively it is implemented, but sure sounds like a cool feature. Is something like this possible with the Kemper, Mr CK? Don't really see much of a use for it myself, but just wondering about the science behind it. Seems like something people have been trying to do for a while now.