NiteRider Lightning Bug 100 USB Tail Light $44.95
Be seen out there.
Be seen on the commute with NiteRider's Lightning Bug 100 USB Tail Light. A bright LED lets motorists know that you're on the road, and a USB charging port ensures that the 800mA/hx1 battery is topped off before you leave the office.
The Lightning Bug provides 100 lumens of light on its highest setting, where it'll last 2.5 hours. There are three settings in total, though: High, low, and daylight flash. On daylight flash, this light will last around 26 hours.
The NiteRider Lightning Bug 100 USB Tail Light easily attaches to seatposts with an included mount.