Considering you asked if it was a heel rest, he probably thought you were making a joke. They move your controls rearward. It gives you a sportier riding position and is more comfortable for those of us that like to be forward on our bikes. Less cramped feeling.
Yeah, sorry, I thought you were making a joke and was responding in kind. As happens too often, tone and such get lost on forum posts. My bad and didn't mean to offend, I'm just stoked that someone is looking back in the HD history to bring back what was one of Willie G's more interesting ideas.
It's a fully rear-set relocation, removing the standard foot controls and replacing them with laser cut aluminum pieces about half a foot back and an inch or two higher. I'm excited as it will increase ground clearance for more lean angle, as well as make weight shifting significantly easier which will help in corners as well. I've been a huge proponent of the 750 power plant since release and I think it's the best part of the bike by far. Performance-wise, it's a bit held back by it's relatively mediocre lean angles, especially when pushing hard around corners. For those looking for a more aggressive style of riding, this kind of set up is exactly what we need.
As far as pricing goes, they probably won't be cheap. TuffSide, which sells the Chappell Custom parts, offers a few other options for rear sets on vintage bikes in the $200+ range, but since the market is flooded with those kits, and this will be the first for the XG series, I'm guessing they'll want to recoup the dev cost quickly. The other parts for the Street, specifically the Brat conversion is around $700, but that's really not that bad for a seat, fender kit, brake and turn signals, and the custom seat leveler. Personally, I did that style.