> That is, it reports status and if the server notices it hasn't gotten a report, I get an alert.

I’m working on exactly that, called SecureCoop. Being in IT the lack of notifications on doors was a huge concern. So I (over-)built redundancies and notifications and server monitoring and clustering.

I’m still working out kinks in the prototype but I hope to be selling later this year. Need to take it to an FCC lab to verify that it doesn’t cause excess interference, and then I can sell.