I have pondered this many times. I've always wondered is there a way to only allow the people you allow into your house so random groups of people don't just enter your home? And also yes being able to turn the connection off so people don't barge in at certain times.

The conclusion I've always reached is all of these things probably exist? How? ~Magic. Which isn't the most satisfying answer but yes.

I'm also now imagining like home security people who come and do all the security for the floo - and also probably other security spells around the home? It probably would exist.