As video streaming becomes more pervasive, new tools and services are emerging to track audiences on OTT (over-the-top) video streaming platforms like Netflix, Amazon Prime and Hotstar--something that has not been done before.   Last week, Neilsen, one of the oldest market research firms in the world, said it developed a new metric called ‘The Gauge’ which tracks audiences on streaming services. Using a hardware patch in Wifi routers, Neilson is able to determine when viewers tune in based on data consumption.