I use Spacedesk for this. It supports Windows as the server and Android, iOS, Windows and web browsers as clients (extra displays). It's still in beta, but it

I use Spacedesk for this. It supports Windows as the server and Android, iOS, Windows and web browsers as clients (extra displays). It's still in beta, but it works almost flawlessly. If your wifi chips are good quality, the latency is almost unnoticeable.