Maybe I'm missing something... if Twilio's going rate is $0.01/message, wouldn't it make better financial sense to sit down and just build this yourself? It's not like it requires a bunch of infrastructure...
This has been a bit eye-opening for me. I coded almost this exact feature last week for a project; never made the connection that this sort of thing is business-able.
You need to set the 'Access-Control-Allow-Origin' header to get them to work in Firefox. More info at https://developer.mozilla.org/en-US/docs/HTTP/Access_control...