Android / IOS SIP Dialler Phone SIP-to-GSM

I need an application that runs on Android phones (4.0 or above) and can send/receive calls through SIP (Can use any sip stack like sipdroid) and forward it to the GSM network. The application should then forward the audio and convert from SIP to GSM and vice versa. Full description below. Please review and message me with considerations. If any requirements are unable to be met, please let me know before we make a deal. Summary:- The goal of this project is to develop an Android application that can send calls through SIP and forward them to the GSM network AND receive calls from GSM and forward to SIP. The application should then forward the audio and convert from VoIP to GSM and vice versa. The app also needs to be able to recognise DTMF tones when calls come from SIP. General Deliveries - The application working in APK format - Full source code with detailed comments - Documentation - Detailed manual for compiling and generating the application from source - A SIP client running on phone that connects to the SIP server via GSM data network. - App needs to be self-running without any human needing to respond - App must store and recognise each handset's SIM number Features - Able to run on Android 4.0 and up. - Route call from SIP to GSM (preconfigured SIP client) automatically without human response - Route call from GSM to SIP (preconfigured SIP client) automatically without human response - No manual dialpad for human to dial out. - SIP User ID will be actual SIM number that will be preconfigured - Convert audio from/to SIP and GSM networks - Pass DTMF tone - Record all inbound and outbound calls on database - simple insert statement. - Recognise SIM number and apply to call records - Obtain GSM SIM balance update via USSD. Application Configurations: - Enable or disable the app - Enable to receive calls only on wifi or GSM data networks - Enable to route calls from GSM to SIP (SIP address is pre-configured) - Enable to route calls from SIP to GSM (SIP address is pre-configured) - Must run on background - Read inbound SMS and credit balance update USSD messages - Must be VERY lightweight to run on VERY low / small memory devices - Configure SIP Accounts. Sip Requirements: - Register on Sip Proxy/Gateway - Receive call authenticated by IP, user/pass or no authentication. - Make calls with or without authentication - Forward DTMF digits using RFC2833 or inband - Use codec G711 and GSM - Be able to use codec G729 - Receive through GSM one 1 simultaneous call and rout it to a predefined SIP client Skills required: Android, Asterisk PBX, VoIP An standard SIP client running on a seperate android phone will have to connect to the SIP server that was developed on the other android phone via wifi and an incoming and outgoing call would have to to be demonstrated. Following additional data will be provided: - Country network dial codes and USSD short code to request balance from GSM network (as each network have their own USSD short code). - Pre-configured SIP details