As iPlayer is a BBC product, why do they need detector vans to determine who is streaming it? It is coming from their servers, so the they know (or could know) the IP addresses to which iPlayer is streaming. In most cases this will be the router address of the ADSL, Cable or Fibre subscriber, from which the address could be determined. Even with a detector van, if someone is streaming via a WiFi hotspot, there will be no way they could tell if the users of the smartphones, tablets and laptops have licences at their home address (and the licence covers use outside the home by equipment powered by internal batteries). Similarly with anyone streaming via 3G/4G.