Both Meerkat and Periscope let you interact with any streams you watch in similar ways. The two apps let you like and retweet streams; you’re also able to post comments that the stream broadcaster can see in real-time.
Great for weddings, don’t you think? Can’t make it? No problem, cousin Jim can stream it live to you. Want to see something specific, just tweet out camera directions – ‘pan over to catch the expression of the groom as the bride enters’ ( does that fit in 140 characters??)