If a cell phone were made with a megabyte or so of memory for digital audio, you could, among other things:
1) Allow your listener to listen to music while you have him/her on hold,
2) Easily record parts of your conversation for later retrieval (for use as "evidence," or a dictated shopping list, etc.),
3) Generate fake "background" sounds with convincing fidelity and volume level to be mixed with your voice, for use in creating more convincing excuse calls (see Pocket Excuse Generator),
4) Download voicemail for later retrieval from the phone when you are outside a service area, or want to replay multiple times without consuming airtime ("Agent Ryan, once you locate the bomb on the sub's torpedo tubes, here's how you disarm it: Step 1...")
5) Generate in advance an emergency message to be sent if you need help in a situation where you cannot speak, such as an allergic reaction to a bee sting near the mouth, or a situation where your voice would disclose your hiding place, etc.
6) Download an audio file of your own choosing to use as your "signature" ring sound. Not a tune to be played on the phone's beep tones, but a recorded bell or fully-orchestrated music, or a car horn, or your own voice, etc. (This application gleaned from Johan's annotation of rmutt's "Real Chime" idea).
7) Make your phone emit a personalized signal at the sound of your voice, to help you find it when it's lost -- suggested by rayfo (see "Personal Ringer" link)
8) Other suggestions...?-- beauxeault, Aug 30 2000 [admin: beauxeault didn't run amok on the annotations - this idea was mangled in a database repair accident. (It had been duplicated with an invalid category, and when I deleted the duplicate, I accidentally used a tool that deleted the shared descendant links and annotations as well as the duplicate. Sorry!)]-- jutta, Oct 15 2002 its funny to read ideas from three years ago when this was just an idea and now its basically standard equipment now-- thejaredfanclub, May 16 2003 I had a similar nostalgic experience last week while reading the 1972 print edition of the halfbakery (now sadly out of print) in which beauxeault, in collaboration with blissmiss and thumbwax, came up with an outlandish idea to connect all computers in a huge network, enabling a more efficient method of porn distribution.-- sambwiches, May 16 2003 random, halfbakery