I am developing an app for iPhone. To be honest I am not an experienced developer so I am using an SDK for this task. I am following the instructions of a page that also provides code snippets. According to the page I use the SDK and Adobe Flash Builder. As a novice developer I think that the page (if you are interested: http://www.voip-sip-sdk.com/p_457-vo...tion-voip.html
) gives relevant and understandable information. In my point of view it might also be useful for other novice developers. I only meant to give an advice with my tread and hope someone will find it useful.