Smaller than a BIC lighter, and just about as cheap: the MD80 mini video camera/helmet cam. Photo: RC RockCrawler.
There's not a lot that's particularly remarkable about the MD80 mini spy camera - it's pretty tiny, it records reasonable 640x480 video in AVI format at 25 frames per second, and it can be set to standby for up to 250 hours until it's activated by a sound, making it a good little spy cam unit. It's pretty similar to any number of helmet cam/mini video cam units but for one fact - it costs less than US$25 on eBay, delivered to your door. For the price it's an outstanding product and the sort of thing you could habitually carry around in your car, recording driving conditions for an instant evidence stockpile in case of an accident or incident. And more broadly it's an example of how Chinese design and manufacturing can get a competitive, quality product to market at a price point that absolutely annihilates the competition, to the point where if you're still concerned about quality, you might just as well buy five of the things in case four break. Which they're not doing nearly so much these days.