Newer Samsung TVs have this functionality built-in. HOWEVER, for some reason, their new version of the mobile client (SmartView) doesn't have that feature, so you can either find an older version of SmartView that still has TV Mirroring active or use it on a PC using their desktop app.
While there are boxes that can code and re-transmit video signals (Plex servers, for instance), you still need a valid video input, and most TV's don't have a video output, so you can connect your cable box, BluRay, etc. to the server box, but not OTA TV, unless the server you buy has a built-in tuner (or you have a TV that does support video output).