While I love my iPhone it has been frustrating that there wasn't a quick way to check minutes from SMS. The phone tells you there are two ways to check minutes (which amount to the same thing). One method is to navigate to the phone preferences, then AT&T and finally to the button to check your minutes which actually sends the *646# code to get the SMS message. So there is obviously the option of adding a "View minutes" user to the contact list and bringing it up that way. For me the annoyance has always been that I wanted to send an SMS to get this information.
Sometimes the obvious solution is just a little too obvious. When you invoke either of the prescribed methods you get a message back from 1 (02). It turns out that if you text "min" to 1 (02) you get a response with your minutes. In fact it seems that anything you text to that SMS short code will get your minutes. This makes a couple of things easy... One is that if you have a "conversation" open with your minute balance you can check your balance with any reply. The other is to add it along with your Google, Twitter and other SMS short codes as a contact in your address book so you can SMS to "View Minutes" or "Minutes" or whatever you want to call it, perhaps "Addictive evil phone company overlords"... you get the idea.