Bought some strips of 3M black reflective tape on Ebay and I am very pleased with it. Without headlights or flash hitting it, can barely tell its there (on black surface). I put some on helmet, under tail of bike and on backpack. Will definitely be more noticeable at night when cages come up behind me.
Without flash
2013-09-22 22.20.24.jpg
With flash
2013-09-22 22.22.05.jpg