We like to terminate calls via SIP to the phone, then making the phone's second GSM module to make a mobile call and switch these calls together. It is like a one sip-to-GSM gateway (see [login to view URL], [login to view URL], [login to view URL], [login to view URL] ).
The user of the smartphone shall receive a portion of the revenue made.
See pdf attachment for more details. This is a short draft version. A more detailed version will be published later.
There is also a lot of support and future development after the first implemenation which could be a full time job.
Developers without extensive experience in SIP, VOIP and GSM do not need to apply. Sorry, waste of time, you and us.