Kobra's Wi-Fi OBD-II car code reader and scanner is down to $13.29 with code ALUA3DVB on Amazon. This is the best price we've ever seen on it. The last deal we shared on it was about five months ago and that was a little over a dollar more expensive than the current deal above.
Kobra's car reader can connect to your phone via Wi-Fi and is compatible with iOS, Android, and sure, for the one or two of you still holding on, even Windows phones. Once connected, you can unlock all the information on your car's performance. It also supports several available apps, like DashCommand for iOS and Torque Pro for Android. Kobra also promises a one-year money-back guarantee if you aren't happy with it.
Kobra has a couple other readers on sale. This OBD-II scanner works via Bluetooth but only on Android and Windows phones. Get it for $8.42 from $12.95 with code 4SMI89DJ. It's a little more convenient if you are on one of those platforms.
If you don't need all the smartphone data collection and Bluetooth connections and just want a simple plug-and-play code reader, this Kobra scanner is down to $13.87 from $18.49 with code 6AYGQKGA.
You can also go for the Automatic Pro OBD-II car reader on sale for $109.99. This thing comes with 3G connectivity and tons of fantastic diagnostic tools that make it worth the upgrade.