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??)