Remember this picture from Back to the Future?
From a technical standpoint, it could work really well. You already pause for a second or so before you click the shutter button, lining it up & waiting for the person(s) to be ready; so it already has some good data to fill in the background where you want to ‘erase’ people, from when they weren’t ther. It just has to do a ‘difference’ filter to find things that changed over time, and overwrite those areas in your final photo with data from the adjacent shots.
Awesome! I hope they release an app, rather than lock it in to any single platform or manufacturer’s devices. They would make a killing, and everybody would be happy! Including me! I already have 4 different photo apps I use on a regular basis to post-process photos for various reasons (and no, not to ‘hipsterize’ them). This would be a welcome addition!