How Do You Locate That Access Point?

parp asks: "As an IT Manager I'm concerned about unauthorized Access Points being installed, or users who setup wireless computer to computer networks. How do you find the exact location of these devices? I've tried walking around the office with a laptop watching the signal, but the signal monitors that are included with most network drivers are very limited. The signal could be upstairs, downstairs or right around the corner, but I can't find it. Results of web searches I've done just tell you how to find a signal (wardrive), not the source. I'd be interested in any software or hardware device that can locate the device within a few feet."