I once went to my brother-in-law's house and knocked on the door -- no answer. He knew I was coming, but apparently he was in the basement and didn't hear me. The door was locked, and I didn't wanna bang the door down 'cause I knew it was the kids' naptime. So I called him on my cell phone.. busy.
So I figured he was piddling on the internet, and didn't realize what time it was. So I logged on to my phone's web browser, fired up AOL Instant Messenger, and sure enough he was online. Of course it took about 2 minutes to type "answer your door!" on a the 9-digit keypad, but it still worked. Of course, I never "needed" it before or since, but that one time it was nice to have.
