Need an App to use smart android phone as an GSM voip gateway 1 port - open to bidding

hi, I want to make a thing as follow: we looking for an APP that can use the android phone as an GSM VOIP gateway The smart phone connects internet 3g / wifi. It has a SIM card. When Users install the App, they input their phone number and SIP account (hostIP is hard coded), these information will be deliver to Asterisk admin. When this App is active, incoming calls of the SIM card will be forwarded to the SIP. So the smart phone will be a gsm goip, its SiM number is like a DID. Please contact me at dinhhien2006@[login to view URL] Thanks all