Google is taking its sweet time adding new features to Google Voice, but it looks like some big pieces of the puzzle are finally starting to fall into place. Google finished rolling out incoming number portability to all users this past January, and now it looks as though it may soon begin tying in VoIP services. Last week, Gizmo5 users began receiving notification emails saying that the service will soon be shut down. Now, VoIP blog Disruptive Telephony has discovered that VoIP calls can be placed to a Google Voice voice number by appending “@sip.voice.google.com” to create a SIP URI. BGR tested the service earlier today and we could not get it to work, suggesting that Google may currently be rolling out the functionality quietly. This is just the first step in creating a full-fledged VoIP service for Google Voice, but it’s an important first step and one that users have been waiting for since Google acquired GrandCentral in 2007.