I recently read that the Volt will supposedly have a secondary "horn"/noisemaker the driver can switch on to alert pedestrians. It will be a 'non-automotive' noise though (at least until it gets associated with the Volt... if they actually build it
).
I plan to put a bicycle bell in the ForkenSwift. I've had a couple of occasions in parking lots where a pedestrian has walked in front of me, and I've just come to a stop and let them go by.
In those situations, I don't have the heart to beep the "regular" horn at close quarters and give them an aneurism when they turn and see a car RIGHT THERE.