I'd love to get a setup like this with voice calls also supported. I'd like to be able to recieve my calls and texts on any device as I can with email/irc/matrix etc
If you don't absolutely need this to originate from a mobile subscription with your name on it, you can for far less money get a DID ("direct inwards dial"; the term colloquially means a virtual mobile number) with any of the numerous VoIP providers out there. Most of them not only provide in- and outbound calls on those DIDs, but also ditto for SMSes. The interface for voice calls is almost exclusively SIP, and for SMSes it's usually an HTTP-based API.
If you go this route, make sure you absolutely know how to, and that you absolutely lock this down. SIP toll fraud is still a problem and if it happens to you, it can get destructively expensive.
Common sense obviously applies. With a cell phone, don't call back to unknown numbers ringing once or twice ("wangiri"). With a SIP trunk, don't allow remote anonymous access.
This is pretty interesting, I'm going to give it a go setting something like this up with ejabberd and their asterisk fork, that way I can use my own sim cards.