Glad I’m not the only one 
I just bought a new ‘smart’ TV and really wish we had smarter routers - that track traffic by device and give us a report of activity or the ability to see what data they are or might be sending out.
Currently some routers do give you some nifty features and I use some of them - for instance I have a wireless printer which is connected to the network via wifi but I have blocked internet traffic for the device (so it can never leak any documents/data externally). I can also create isolated wifi networks, so devices on them can access the web but can’t access other devices on my main network (so separate to Mac/iOS devices). This is also handy for guests.
Shame that Apple’s AirPlay requires an internet connection and doesn’t have an option to stream from the device internally…