Doug, as someone on the other side of the badge, let me tell you my take on it:
It is ALWAYS a good thing to inform any officer that contacts you when you are armed. Blues Man's statement is a good one to use; as it has been said, it puts us at ease, and makes the contact much more sociable--and even friendly.
In some states, you don't HAVE to let the officer know...but, here's an example of what might happen:
Officer: "Excuse me sir. May I speak with you for a second."
You: "Sure thing. What's going on?"
Officer: "It's a nice night. I don't see many people here after hours, and quite frankly, I'm a bit curious."
You: "That's OK. I took a shortcut tonight to see a friend."
Officer: "OK. May I see your ID, please? I need it for my report; every time I contact someone, I have to document it."
(You didn't bother to tell the officer that you are packing; as you reach for your wallet, your shirt tail falls away, and--guess what?)
You: "No problem, Officer. Let me get my..."
Officer: "Hold it, right there! FREEZE!"
You now find yourself staring down a gun muzzle.
Officer: "Hands on your head, RIGHT NOW! DO IT!"
You: "But--I was just..."
Officer: "DO YOU WANT TO GET SHOT?! HANDS ON YOUR HEAD! NOW, TO YOUR KNEES! FLAT ON YOUR STOMACH, NOW! HANDS OUT TO YOUR SIDES! CROSS YOUR ANKLES! DO NOT MOVE, OR YOU WILL BE SHOT!"
Officer, in radio: "Roll priority backup, I have one at gunpoint."
Now, here's the second part, after the officer asks for ID, done right:
You: "Officer, I'll give you my ID, but I want you to know that I have a permit to carry, I'm armed right now, and I'm carrying, right side. I have to reach past it to get my wallet. What do you want me to do?"
Officer: "OK. Just keep your hands in sight for me. What's your last name? First, and middle initial? OK, your birth date? Thanks. Hold on a second, I'll be right back with you."
Officer, into radio: "Dispatch, I have a name: Last of Peg, first of Tent, middle initial B, date of birth, 06-07-2009. Also, verify last four digits of SSAN, please.
The officer then asks for your last four, and asks you to hold on for a second, while he or she backs away a bit further. You see the officer speak into the radio for a second, and then return.
Officer: "OK, your CCW's current, and you are clear and current. Be careful, and I hope you make it to your destination safely. Thanks for letting me know about the permit and the gun, OK?"
You: "OK. See you later"
The officer watches you until you get out of sight, then clears and goes back on patrol.
(And, yes, I've had both scenarios!)