Strike Industries is showing an interesting new sling mount. It has some fairly standard features like a QD swivel socket and a loop for use with MASH and Snap hooks but the real story is the unique form factor that gives it an extremely low profile. It is so low profile that it actually sits flush with the top of the very rail that it is mounted to. I think this design has a lot of merit and should be useful for mounting slings in otherwise hard to mount places like under the objective end of an optic.
Check out Strike Industries.