Looks like this is "bring your own number". It's neat, but I wouldn't trust this site to stay up under any kind of stress, which means my number would be erratically dead. If the source is available though, this is neat enough I'd consider self-hosting it.

It's hosted on a paid Heroku instance, our own company number is served by this. The server didn't break a sweat with this HN traffic.

That's not reassuring. It's a free service that could shut down at any time. It's lovely, but I would never use it directly for anything serious unless I could pay for it.

it's available in more countries than the US