Henry_Best:
I agree that that is what he probably should be doing, but we have no indication of why he needs/ wants a two way switch.
It is explained in his other post. He wants to do the old "remote control from a smartphone" stunt - or something like that (various "instructables" or similar on this topic). But of course if you do this from a distance, you need to know whether you are actually turning it on or off, or if you need to.