Inspired by TTSNotifier on Xda-Developers (http://forum.xda-developers.com/showthread.php?t=550839), this widget allows you to enable/disable voice notifications for incoming calls and sms'.
I use it primarily for while driving so I won't have to fumble around with the phone before deciding if I should pull over and answer, but I imagine it would be quite useful if you're in the middle of something and don't want to go through the effort of stopping, checking the phone, grumbling and going back to what you were doing while cursing about not wanting to be disturbed by that person now.
This requires Android 1.6+ and Donut Text to Speech data to be installed.