People who commute by bicycle don't have to remove their pedals, racks or fenders when they park in public ... so why should their lights be any different? Well, because most battery-operated bike lights come off with the simple flick of a quick-release, or the turning of a single bolt. Massachusetts-based Gotham Bicycle Defense Industries, however, is attempting to address that problem with its Defender bike light. Not only is it theft-resistant, but it's also waterproof, and it looks like the light Dirty Harry would use - if he rode a bike.
Unlike most handlebar-mounted systems, the Defender doesn't consist of a bolt-mounted base and a quick-release light. Instead, both sections are formed out of one continuous piece of aluminum. It also can't be removed using a standard hardware store-issue screwdriver - a much-less-common security screwdriver is required, and comes with the light. While it's possible that a dedicated thief might be packing such a tool, it's highly unlikely that the passing opportunistic bike parts-pilferer would have one on hand.
The light itself incorporates six "ultra-bright" LEDs powered by three AA batteries, which should provide about 50 hours of steady illumination (or 100, in flashing mode). In its present pre-production form, the total light output is sitting between 40 and 60 lumens.
A tiny Allen key is necessary to access the battery compartment ... again, not a guarantee that the batteries won't be stolen, but enough to thwart the "Hey, I wonder if I could take this" types. Additionally, three internal silicone gaskets ensure that the light can be submerged up to one foot (30.5 cm) underwater, so it's safe to leave attached in the rain or snow.
The inventors of the Defender, MIT grads Brad Geswein and Slava Menn, are currently raising funds for its development on Kickstarter - they've already surpassed their goal, however, so it looks like the product should make it into production. A pledge of US$50 will reserve one for you, once they're ready to go (the estimated retail price is $70). A tail light is reportedly in the works, too.
More information is available in their pitch video, below.