GrandCentral is now known as Google Voice. It is one of several Internet Voicemail Services. Google Voice enables users to send text messages, customize voicemail, read voicemail text transcript, and more.
Google's voicemail service is available for Gmail users that have another phone number to register with the service. Google provides the service without charging money. Their revenue comes from the data they harvest out of your calls and text messages that you send and receive through the service. They use data gathered to create targeted advertising.
There are privacy concerns using Google Voice. Depending on how sensitive your communications are, you may wish to reconsider using Google Voice. If your communications are not private then the service can be very useful. It makes a great front end number for a new business.
Hacking Google Voice is about ways to customize the service to better serve your needs. This includes software that works with Google Voice for your PC, as well as your smart phone. Hacking Google Voice is _not_ about educating you on how to invade another user's privacy.
Google Voice cannot directly place calls. Some recommend using Google Voice with Skype for a complete multi number, Internet VoIP telephone service.
Web Front End
The web front end works best when used in Google Chrome web browser. The Google Voice Front End can be reached by the following URL:
You must have a Google Login (such as your gmail login) to use Google Voice. It must be associated with a land line or other phone service so you can place calls. Only one Google Voice number per gmail.
Google Chrome Widgets
Software for the PC
Android Apps