title: Create a SIP / VoIP phone routing application
body: <p>At the office we have a hosted VoIP telecom system. We use SIP / VoIP phones and recently we have been playing with some SIP clients on our iPhones. Connecting with these 'other clients' works fine and that made me think; can I do some programming on this? 
  I'm not really interested in making a SIP client / soft phone, but more something like a 'soft receptionist'. </p>
  
  <p>Is there a library I can use in a .NET ( + code examples), which enables me to create an application that can see who's calling and redirect calls depending on that incoming phone number?</p>
  
  <p>Or, when there is some OOTB software available I'd like to hear about that too. </p>