title: Are there any other SIP implementations for iPhone besides Siphon?
body: <p>I'm trying to build a SIP app for iPhone 4 (iOS 4.2).
  Tried to use <a href="http://code.google.com/p/siphon/" rel="nofollow">siphon</a>, but no success (<code>IOKit.framework</code> is missing from the sdk, <code>libg729a.a</code> is also missing).</p>
  
  <p>Is there any other way to implement SIP for iPhone?</p>