I personally use a PB Superflash on my seatpack but just added one of these for a little extra added visibility.. I just wrap it around my rear triangle, just above my rear brakes.. Nathan Acid Reflex Snap Band LED Light.. I also use it for running at night, just wraps around my arm.. It uses 2 small watch batteries for the leds.. It gives you 360 degrees of flashing leds...

http://www.pricepoint.com/detail/169...-Snap-Band.htm