Cross-Platform Mobile SIP Application Development using sipjs or any other library

We requires the development of a Mobile SIP. The Mobile SIP app will be built with any open source SIP stack protocol that is preferred by the developer. TheCodec Systems Limited could also help in choosing a SIP stack protocol in the event that the developer doesn’t have anyone of their choice or have one that doesn’t meet the specifications and capabilities described in this document. The Mobile SIP app will be downloadable from all app stores, meaning it will support mobile devices that runs firmware such as Android, iOS, BB, Windows Mobile, etc. (We will like it done with Android first, since its majorly used these days). The Mobile SIP app will be designed with simple interface (just like similar SIP apps) and capable of the following; 1. Once clicked, it should be able to retrieve the IMEI and MSISDN from the mobile phone it’s installed on, and send those parameters to our SIP server for initialisation and registration. The idea is to allow an easy & seamless registration to our SIP server. 2. In case it can't retrieve the MSISDN from the mobile phone, the MSISDN be entered on a text field on the app. The developer could also suggest a better way of achieving this seamless initialisation as described in 1 above. 3. The Mobile SIP app could also optionally send either a direct authentication code or SMS an authentication code to the SIM card, so the user can enter the code to complete the initialisation and registration process. 4. Once registered with the SIP server, the Mobile SIP app should be capable of dialing (with a regular dial pad), and sending DTMF digits just like other SIP related mobile apps, during an established SIP session with the server. During an established call, the interface should display the usual “speaker”, “Mute”, “Hold”, “keypad”, “Statistic”, etc action buttons. It should also be capable of custom dial buttons to be designed on the Mobile SIP app interface. It should also have a call log for dialed history. 5. The Mobile SIP app should be capable of masking DTMF number entered as a response from the SIP server, during a SIP session with the SIP server. e.g. when prompted to dial a code by the SIP server, the code entered via DTMF could be made to mask as **** or blank as the case may be. This should be configurable to allow us set which code should be mask and vise versa. 6. The Mobile SIP app should be customisable. We should be able to customise it for any SIP related purpose as we so wish. Meaning we will have a copy of the source code. This Mobile SIP app is not intended to be used for a SIP to SIP calls between users using the Mobile SIP app, but we could consider that in future. The purpose to which the Mobile SIP app usage is intended, will be determined from time to time.