Whenever my cell phone rings, I know who’s calling. And I usually know what they’re calling about as soon as their picture (or name) appears on the display.
I’d like to see companies do this for customer service. I ranted earlier about United’s voice recognition system. Improving that system is one step, but I’d like to see them go further.
99% of the time, I call from my cell phone. Let me register that number and use it to provide better service.
Today, when I call for flight information, I have to enter my flight information. Use my phone number to look up my itinerary for today and when I ask for flight status, tell me about my flight. (No, I won’t be wanting the flight status for the flight 3 weeks from now.)
If I need to speak to a representative, use the caller ID (technically, ANI) to bring my itineraries up on their screen. Instead of having to fumble for record locators, flight numbers or my Mileage Plus number, have it happen automatically. You’ll save me time and save steps for your call center reps.
Of course, you’ll need to ask a basic question or two to verify it’s me and not someone who found my phone, but you do that anyway.
Rakesh Agrawal's blog 
The spirit of your idea is dead on. (A 21st century Dante most certainly would include Voice Recog and Voice Prompt IPCCs in the lower levels of the Inferno.)
BTW, it isn’t necessary to have the physical phone to gain access to ANI enabled apps. All you need is the phone number.
http://theolagendijk.wordpress.com/2006/09/01/paris-hilton-likely-hacker-of-lindsay-lohans-voice-mail/
One reason not to have your VM password turned off, although not many humans are so good with passwords.
http://www.iwar.org.uk/news-archive/2004/04-20.htm
That said, just about any unintended vulnerability created by useful applications can be overcome by adhering – from the beginning – to disciplined planning and development methodologies (in this example, strong password AuthN). Unfortunately, humans (particularly Americans it seems) aren’t so good with discipline either.
“What Americans are Made of”, Josh Hammond and Jim Morrison identify 7 US cultural forces that trample good intentions to do things (e.g. design) right the first time.
http://www.mfinley.com/experts/hammond/HAMMON1.HTM