I searched here for sms api, but could not find anything. Is it even possible to send/read sms messages on Firefox OS?
Because of its high-impact security implications, the WebSMS API currently is only available for certified applications on Firefox OS (see WebSMS on MDN).
Certified applications are the ones included in the operating system itself, so - as a third party developer - at the moment you can not create applications that can use this Web API. Accessing the SMS API is a much requested feature, though, so there is work going on to make this possible in the OS on the long term, but not in the near future.