Contrail is such a cool idea! A small device is attached to your bike marks your rear wheel with chalk. When you ride a trail is left in your wake. When a lot of people ride with contrails in a community, bike paths and trails that are commonly used emerge. It helps cars know to look out for cyclists, it helps urban planners know what routes and streets are being used, it helps cyclists know what routes other cyclists enjoy. I would love to get a bunch of people in my community using this device.
I first saw contrail about six months ago when their concept was passed as a link around Synapse (maybe it made to the Wall of Cool then, I'm not certain). Recently they sent out a post explaining that they were trying to raise money for a prototype run... YOU CAN HELP! Click on the link and check out their Kickstarter video. Pass it on if you think it's cool... and maybe, just maybe you can send them money too :-)