The Motion Stills app combines a couple pieces of technology Google already featured in Photos, like video stabilization and auto-creating gifs from bursts of photos. According to Google, the new Motion Stills algorithm "uses linear programming to compute a virtual camera path that is optimized to recast videos and bursts as if they were filmed using stabilization equipment, yielding a still background or creating cinematic pans to remove shakiness." In other words: you've got a virtual tripod or steadicam rig built right in.
In addition to keeping your shots steady, the algorithm does a lot of heavy lifting to identify moving objects in the foreground to keep them isolated from movement in the background. And for a handy bonus, it will also pick an optimal loop point to cut off those embarrassing moments when your video ends with you putting your phone back in your pocket.
The app works its magic on your phone, so you won't need a data connection to create your latest masterpiece, but you will, of course, need a signal to share it to your social network of choice. Motion Stills is available on the App Store.