The Mail Light hardware could easily be modified to turn on some rotary warning lights, such as these lights from Woot.com.
The example pictures below show the modification of a set of these lights to be driven by a U401 which works just as well as the U421:
Inside the lights:
Modifications to drive the LED and motor on their own:
Light attached to a development board that contains a U401:
U401 and driver wired up to operate the rotary light: