The patent, if implemented, would note where you had stopped watching a video on any connected device, and would automatically set that as the start time on a different device. Watch a movie over lunch, then pick up in the middle when you get home on your iMac or Apple TV, without spending the excruciating 30 seconds it takes now to find exactly where you left off.
The patent also includes various forms of distance tracking, allowing for various sync operations to occur when two devices come within wireless range of each other. Apple specifically describes (in legalese, but comprehensible with a cup of coffee and three aspirin) an Apple TV device detecting an iPhone coming within range, and then picking up the latest data from a central server.
Left somewhat unclear are the protocols being considered; Bluetooth is mentioned in an example, but this technique could easily apply to Wi-Fi discovery. Alternately, there’s no technical reason why Find My iPhone couldn’t allow your computers to find you instead, and start downloading a new movie when you’re still 15 minutes away from home.