It's already supported within transform, was previously known as 'tweak mode' and for some odd reason was a compile time option. This brings it to a user preference (in 'Edit Methods' section). Basically it means that you don't need the extra click at the end to confirm a drag-move transform, if you're already dragged, you can just let go of the mouse rather than needing to click again. It's a lot more comfortable when you're used to using other applications as well as blender, and much more sensible for tablets. This started life as patch #7144 by Ed Britton, but this implementation has been changed considerably.