Google Voice already offers pretty granular control over your contacts list, allowing you to send certain callers straight to voicemail, or set certain ringtones or voicemail greetings for contacts in a specific Google+ circle. Today, Google's announced a few new groups that let you have more control over people calling you who may not already be part of your contact list. For starters, customization in your address book now works by exclusion — you can set specific ringtones, greetings, or screen calls by people not found in a specific group, circle, or your address book at large. Furthermore, you can also have specific settings for anonymous callers (callers that don't have a caller ID and show up as "restricted" or "unknown"), which helps you keep better tabs on calls that might be better left unanswered. Google says these features should be available today, so go ahead and start tweaking your Voice settings.