I am a big fan of Custom SLR's C-Loop. The one and only drawback to this sling carrier is you have to remove it in order to mount it on a tripod. As I mentioned in the C-Loop review the Split Strap is the most comfortable strap ever.
At CES Custom SLR revealed the M-Plate. The M-Plate allows you to mount both the C-Loop and a quick release tripod plate on your camera at the same time.
I am not sure about the release date or the exact price, but I do know that I will be getting one as soon as they are released.