Bicycle lights may not exactly be a problem that needs solving, but the following can be said about most of them ---- they're easily stolen if left on an unattended bike. People riding at dusk can forget to turn them on, and those same people can forget to turn them off when they reach their destination. Well, the makers of the Blink/ Steady Bike Light have set out to address all of those shortcomings. The waterproof  Blink/ Steady is so far only available as a tail light, although a head light is on the way. It's fixed onto the bike's seat post. A built- in photosensor  tells when it's become dark enough for the light to be required, and allows it to come on once you begin the riding. According to the producers, it isn't fooled by things such as headlights or streetlights. The light also contains an accelerometer, also known as a motion sensor, which can tell when the bike is in motion. Between the two sensors, this means the light will come on only once it's dark enough, and the bike is moving. Even when stopped at red lights, the small movements of the rider will reportedly be enough to keep the light activated---- it'll go out after 30 seconds of complete inactivity. While this does mean that the two sensors are continuously powered up, they go into a very low---- power sleep pattern when the bike is sitting, unused. Light is provided by two5- watt LEDs, seeable over a range of 180 degrees. And power comes from two AAA batteries, which provided up to 200 hours of continuous run time. The designers and engineers behind the Blink/ Steady are now raising money for its commercial production. About US $95 will get you one if they become available. Why is there an accelerometer in the Blink/ Steady Bike Light?
To protect the bike against water. To tell if the bike is moving. To make the bike easy to ride. To judge the speed of the bike.