There are reasonably priced headlight modulators on the market. I installed one and what it does is flash the high beam 4 or 5 times per second. It has a photo sensor so it will not work dusk to dawn to keep it legal. It raises peoples awareness of your proximity quite a lot from the comments I have received.

Yep.....I have mine passing switch wired into an Emergency flashing LED just below my headlight.  It is a split emergency LED with 2 white and 2 yellow LED's that flash at whatever pattern you set it for.

You need to go into the wiring harness....about half way between the handlebar and the split where part goes to the headlight.  You will find a second yellow wire spliced into the yellow wire from the high/low switch on the handlebar.  You then cut the wire from the passing light, and then splice a wire onto it and take it to whatever you want to power.

And yes......you could more easily wire the LED to the horn if you didn't mind them both running at the same time when you push the button.

Here is the thread where I posted the addition to my bike.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1372162554/0

CA driving code says:

Motorcycles: Headlamp Flasher
    25251.2   Any motorcycle may be equipped with a means of modulating the upper beam of the headlamp between a high and lower brightness at a rate of 200 to 280 flashes per minute. Such headlamps shall not be so modulated during darkness.
               Added Ch. 35, Stats. 1980.  Effective March 7, 1980