I wonder is there any way to make Google Map Marker to pulse? Like here: http://plebeosaur.us/etc/map/
This may partly answer your question. You may use animated polyline like in this example: https://developers.google.com/maps/documentation/javascript/examples/overlay-symbol-animate
Of course you may build more sophisticated animations if need. You may also switch with setInterval() images (transparent PNGs) markers or its css styles (box-shadow as per your example) so it will look as an animation.