Up until the latest AI wave, Twilio was almost in every thread about a new service!
https://www.twilio.com/labs/twimlets
I use the "Forward" one for calls.
For SMS, it used to be not too complicated - I would host a file directly on Twilio (using a Twilio bin) to forward the SMS to another number.
Recently, sending out SMS's has become a lot more complicated due to compliance (Twilio wants to make sure you don't spam people - but the burden on small developers was just too much for me, after ~2-3 months of back and forth emailing with them to get approved)
I've switched my SMS forwarding to use https://pushover.net/ . I use Twilio's hosted nodejs platform to get the incoming SMS message, and use Pushover's API.
It's potentially brittle-ish overall (lots of pieces) but it's also been working for years.
A native mobile app that would let me just get calls and sms for my hosted Twilio phone numbers is really what I'm asking for... :-)
I'm a bit locked in for now (and am dreading transferring all the numbers I've accumulated) but yeah. Thanks for the perspective
In some countries even phone carriers may offer SIP trunking for individuals. But most often they work with a handful of resellers, who in turn have smaller and smaller companies as their clients. So, if you only need to support a small volume of calls you'd find that your prices per connection or per minute are higher.
Similar to sending email, telephony is a business of volume. The more call you make the less your prices are going to be. I worked in telephony space for a few years, and it's a fascinating industry.
It's just an XMPP gateway, so you can use any XMPP capable chat client or gateway you want. XMPP isn't the worlds best protocol, but it works fine.