You mean like this? I clipped off the belt and attached it with velcro to my backpack.

And I have had more drivers, daytime and nighttime, and cops pull up beside me and tell me that it really helps. Apparently a lot more drivers than you would ever think actually recognize that as being a slow moving vehicle/warning that there is something up ahead that I should be paying attention to signal.

When I go out on a training ride along the same routes I get a different level of support from drivers as I do when I am commuting and wearing my backpack.

I think it cost a whopping $8 or something like that too, so it has definitely been worth the money for me.