Mobile VoIP SIP Dialer for Android and iOS

We are looking for a mobile VoIP dialer application to be developed to work with a TekSIP server. The client must be based on SIP, and it must work on Android (versions 2.3 and above) and iOS (versions 4.0 and above). The iOS version should include iPhone, iPad, and iPod Touch. For Android, the client app must support both phones and tablets. The look-and-feel must be customized to support our business needs. When the user is in range of our wifi network, they will start the client app and it will automatically attempt to connect to our wifi network. The wifi network credentials will be prefilled with the authentication parameters that we will provide. Additionally the wifi setting parameters must be configurable. For first-time activation only -- if the VoIP parameters do not exist: a) Prompt service info and agreement (continue or cancel); b) prompt for user VoIP parameters and Account info for billing: Phone number (pre-populate if possible), Display Name, Billing Account ID and Date of Birth (mmddyyyy); c) The server will validate the user, and will return the SIP server IP address, domain, and user password if the validation is successful. The client app will save these parameter settings in the app profile. The protocol used to communicate with the back-end server to submit and retrieve the SIP server info is via a Web Service call. We will provide the web service app in the back-end server. The app client will attempt to REGISTER to the SIP server. Re-registration should be sent after every 5 minutes (configurable parameter). The dialer must include: a) Dialer, b) Call History Log, c) Contacts list, d) SMS text messaging. We will work on the look-and-feel of the user interface and user experience of the app with the developer as part of a milestone. The client must comply with SIP RFC 3261. It must work with the TekSIP server. The text message should function similar to the standard text message screen commonly used in the telecom industry and smartphones today. The text message will be based on SIP (SIP MESSAGE method). It should store and display previous messages. The client must support G711 and G729 codecs. The loading page should display our logo. We will require the source code as a deliverable for review. The client will allow the user to select a contact from their phones integrated phone book, and if the app is running it will dial that number. You must have a previous experience writing a mobile VoIP (SIP) dialer. Preferrably using the SIP stack from Mjsip. As part of our selection process, we need to see a similar work that you have done in the past. Thanks!