Riding a bike on roads populated with cars makes communicating actions, like when you're braking, an important part of cycling safety. Instructables user tomatoskins shares a way to add a taillight to your ride that lights up when you hit the brakes.
We've shared some bicycle safety hacks before and this one is just as useful. The setup uses a modified blinking bike taillight, some copper, wire and a lot of zip-ties to hold everything in place. The build isn't terribly complicated, but keep in mind that some soldering is required. For a complete guide, check the link below.