Aren't there now motion sensor cameras you replace where you bell ring is, and they immediately contact your cell so you can see who is at the door? The system allows you to also talk to the person via a microphone. If the person looks suspicious you can just say, "Leave my property now. The police are on the way".
I see the ad on TV often and it seems to me the voice comms to a stranger could be a good deterrent. Plus, I believe they record the encounter. I'll try to find the name.
My Ring doorbell does that.
There have been events where I have answered my front door while I am in another city. The person at the door had no idea that I was not inside.
We subscribe to the Ring monitoring. It is very inexpensive. There are sensors on all the doors. And their default base station includes phone dial-out on a common phone network. Thus, when my house wifi went out due to a power failure, my Ring sent me a phone message telling me the wifi and power were down. They were still capable of dialing out to Ring security people if there had been a door opened. Fifteen minutes later, I got a text message that everything was back to normal.
Have you ever seen an ad for one of those cameras with a black guy stealing a package?