Someone watching a cable series at a friend's house can finish the program at home or on their mobile device, schedule their DVR to record an episode, even record the full season, just by sampling the screen for a second or two.
While being able to schedule DVR recordings from your mobile device is nice, an update currently being pushed to some Comcast DVRs is adding the ability for users to check exactly what shows are stored there from an app or web browser.
All three perform the same basic function -- they let you stream TV from your cable box (digital or analog), satellite receiver, or DVR to a computer or mobile device -- it's just that each is aimed at different segments of the market.