What is the "backend'for this? I mean do they use something like twilio or something else? I am asking cause I think most such services use SIP instead of xmpp, although for messages xmpp might fit better.
The backend is Bandwidth. Since JMP uses an actual carrier instead of a reseller like Twilio, it is easier to fix issues and get questions answered, as there is one less level of tech support indirection.
It also means JMP's costs are lower (Twilio is extremely expensive) and gets more features (Twilio doesn't do group texting or messages to short codes).
While SIP does support messaging, it is extremely limited: text-only and single recipient (no picture messaging or group texts). So XMPP is a much better fit, as all the texting features people expect can be implemented over XMPP.
It also means JMP's costs are lower (Twilio is extremely expensive) and gets more features (Twilio doesn't do group texting or messages to short codes).
While SIP does support messaging, it is extremely limited: text-only and single recipient (no picture messaging or group texts). So XMPP is a much better fit, as all the texting features people expect can be implemented over XMPP.