The U.S. Patent and Trademark Office published a patent from Apple today that details a way for iPhone users to tell if other users are available before they even attempt to make a call. The patent is called "Methods to determine availability of user based on mobile phone status," and describes how it would use similar server-controlled status updates to instant messaging products like iMessage in order to clue people in on when might be best to call their iPhone-owning friends and family.
The invention is designed to make it easier for iPhone users to anticipate other user's availability. Instead of calling someone only to get voicemail, you would be able to tell if they had their phone in Airplane mode, were going without reception, or just couldn't come to the phone at that point.
In order to make this happen, the iPhone would connect with an Apple server to make it clear what its status is. Information including signal strength, battery life, and location would be made available, as well as the phone's mode, including Normal, Airplane, or Vibrate. This way, when someone tries to call you, they'll get this information on the screen before they complete the call.
It's sort of like being able to see somebody's status on an instant messaging service before you send them a message. While Apple acknowledges caller ID systems can offer some level of call screening information, it argues that's not enough to be truly helpful for callers. By making a user's "state" readily available, callers get a full picture of where the callee is at and whether they're available.