Some unified messaging (UM) systems have the facility to call your phone and play a voice message from your inbox. They provide this function in case the PC you're using doesn't have audio, or in case the use of speakers might disturb others nearby. The idea is that you click a button in the message and select a phone number. The phone rings and the UM system plays you the message.
So next time you're in a boring meeting and you need an excuse to leave the room, try this: Subtly pull out your wireless PDA, connect to the UM system, and instruct it to play a message to your cellphone. Your cellphone will ring with an "urgent" call -- now you have the excuse you need to take a break from your boring meeting.
... Richi Jennings, with thanks to Microsoft's Dinar Somani