Does anyone know of a SIP application that integrates with a VoIP phone system? I downloaded SIPdroid, but you have to use VoIP service through PBXes.org. I have a VoIP phone system (ShoreTel) in which I can set up SIP extensions. Assuming I have an app on my phone (iPhone has this app), I can walk into my office, have the local wireless network connect to my phone via Wi-Fi, and automatically assign my desk extension to my phone. Therefore whoever calls my DID or my desk extension, it will ring directly to my Hero. Any ideas?