PLX Kiwi, as seen above, is a plug-in device that analyzes how you drive and teaches you how to do it in the most gas-efficient way possible. Although you could easily accomplish the same thing by yourself after reading some tips online-Kiwi says you get about 20-33% improvement in your MPG-it's easier to have something always there reminding you to not gas so hard or drive so fast or brake so much. There's also "challenges" that teach you how to do this, which could be a fun distraction when you're driving along a long stretch of highway. On the other hand, the Kiwi has a MSRP of $299, which takes a bit of savings to earn back. [PLXDevices]