A couple of years ago Microsoft released a Miracast Wireless Display Adapter that could be used to wirelessly send a tablet, laptop or phones display to the TV. Microsoft have just announced a new Miracast device that has reduced latency and a new smaller form factor. With the Lumia 950 and 950 XL and Continuum you should be able to use the phone as PC on the big screen and the reduced latency should make it a better experience. It also will be better when mirroring a PC or tablet as the lag can be an issue with Miracast.
So far I have found Roku’s Sticks work the best so it will be interesting to see how this compares. The new Wireless Display Adapter is available to pre-order in the US for $49.95 and coming to the UK sometime in the future.