I am working on a similar project. I have something working for my own needs and a few other families already but a long road to go before making something GA.

You can waitlist at https://havenphone.com if you are interested.

There were three major things I wanted to do differently from Tin Can:

- I wanted to use off the shelf VOIP hardware so if the company ever went out of business I (and any of my users) had an escape valve or could just sell the hardware.

- I wanted to have a code base I could open source. (not open source, yet!)

- I wanted flexibility to offer ATAs (devices that let you connect any ol' "analog" phone)- some of my parent friends wanted cordless "DACT" phones, interestingly.

It has been quite an adventure entering the world of VOIP.

The SIP protocol has so many esoteric options (understandably given its history!) it could make TLS look simple.

My most recent learning is this crazy protocol called TR-069 that ISPs use to configure endpoint hardware like home routers, cable modems, and VOIP phones. https://en.wikipedia.org/wiki/TR-069

Also, interestingly every cheap (sub-$50) phone and ATA I have tried has a built-in OpenVPN clients.

Oh, and one more interesting thing Grandstream ATAs are able to be taken over by the Grandstream cloud service by just providing the ATA serial number and mac address on the back of the device- I did not love that workflow when considering long-term security. (:

If you have $50 and some time to kill you can do it all yourself right now. In voip.ms you can use the phone book and the caller id filter to create a "*" hang-up rule and an "allow phone book" rule.

- https://major.io/p/85-cents-home-phone/

- https://www.voipsupply.com/fanvil-h3w-wifi-hotel-ip-phone-wh...

- https://www.voipsupply.com/fanvil-h2u-black-hotel-phone-v2

- https://www.voipsupply.com/grandstream-ht801-v2-ata

Tin Can, a 'landline' for kids