I currently have one app in the iOS App Store. It’s called GV Places.
Google Voice allows you to have one phone number for people to call, yet have it ring on any number of physical phones. GV Places will allow you to create groups of phones and optionally tie them to a geographical location, which can then be enabled with a single tap, or automatically when the app is in the background.
Due to technical and financial issues, GV Places was discontinued on October 30, 2012. More details are here.