I quickly used some of my REI dividend this year on some Reelight bike lights ($49.93). The unique feature of these is they don’t require batteries. They generate power as your bike wheels rotating, forcing some powerful magnets past the light assembly. It doesn’t take much to get them started. By the time I hit the end of my driveway, they’re blinking.
Unlike the old school wheel-generator I had as a kid, this one is quite and has less noticeable drag. However, it also could be disengaged from the wheel. The Reelight is always on.
This Reelight model can store power which keeps the lights flashing even when you’re stopped. I found they flash for more an a couple minutes after stopping. Of course this means that as you lock up your bike and start walking away, people may say “you left your lights on” — it’s already happened to me.
Yes, they are a little heavy, but it seems like a fair tradeoff in order to have 24/7 increased visibility on an urban bike.
And you never have to worry about batteries.