In late November, 2016, Rolex was granted a patent for a complication that would serve a similar purpose to a chronograph, but with fewer parts, thereby making it more reliable, smaller, and lighter than traditional mechanical chronograph movements.
The basic premise is to have a your normal hour, minute, and second hands (shown as a small seconds in the patent drawings), and then "stored" hours, minutes, and seconds hands. Both sets move in sync until you freeze the "stored" time hands. Then, instead of having a readout of how much time has elapsed as with a typical chronograph, you simply have a display of when you stopped the clock.
Two heart cams then serve to resynchronize the seconds with seconds, and hours and minutes with the actual time. Heart cams are routinely used to zero out chronographs, so they have a long history in watchmaking.
I feel that it's unlikely this makes it into a Rolex watch. (The discussion of why you patent something if you're never going to sell it is for another day.) It's not clear where it would fit in their line, and it seems like most people would correctly view it as a cheaper, less convenient version of a chronograph. It's easy to read elapsed time. It's harder to do watch-math -- It's 8:37 now and I stopped the watch at 7:18. . . It's an hour and nineteen minutes, but it took you longer to get there than looking at a chronograph.
One thing that's notable about this patent is that it relates to a new complication, rather than improvements in materials or reliability to existing components. It's a little out of the ordinary for Rolex.