Aegean Music has released Doppler Dome, a free VST/AU Plugin based on the Doppler effect.
The Doppler effect is something that happens to sound when the listener and the sound source are getting closer together or farther apart. For example, a car sound when one is in the car might have a particular frequency, but the frequency will be lower if the car is moving away, and will be like a record played at a lower speed. If the car passes right by it will be high as it gets closer and then low as it gets farther. Doppler dome lets a user adjust the amount of the pitch effect as well as pan and volume based on distance.
In Doppler Dome, the center is the listener and the sound source moves along a path. Drag the dots to adjust the path's Bezier curves. A MIDI note in message sent to the plugin will reset the path position to sync it with the project.