Performance and apps
By itself, the Kiwi Bluetooth doesn't do very much. However, as an interface for third-party vehicle-monitoring apps, the device allows your phone to monitor dozens of OBD-II parameters. It is only limited by which parameters are reported by your car's diagnostics system. In most vehicles, you'll get engine rpm, vehicle speed, coolant temperature, intake air temperature, engine load, and many more. Engines that use forced induction may report boost pressure. Additionally, if your Check Engine light is illuminated, the Kiwi can relay the trouble code.
In order to make use of any of this data, you'll need a diagnostics app for your Android phone. Fortunately, there are many free and paid apps available in the Google Play Store. PLX itself recommends that you take a look at Torque (free Lite version, $4.95 Pro version), alOBD Scanner (free, $4.99 Pro version), VoyagerDash ($1.00), OBDroid (which I couldn't actually find in the Google Play Store), or Dash Command (by far the most expensive at $49.95), as all of these apps have been verified to work. All of these apps will be able to display the raw OBD-II data as gauges, graphs, or numerical readouts, but some will be able to take that data to calculate values such as torque, horsepower, or fuel economy.
I tested the Kiwi Bluetooth with the basic, free Torque Lite and found that the Kiwi performed exactly as advertised. The phone's interface makes setting up the gauges that I want to see much more intuitive than fiddling with buttons on the tiny-screened standalone OBD-II loggers that I've tested previously. Your experience will vary depending on what app you choose to use in concert with the Kiwi Bluetooth, so try them all and pick the one that best fits your needs.
Additionally, I staged a fault code by removing the test vehicle's fuel cap and driving for a few miles, which caused the check-engine light to illuminate. The Torque Lite app popped up the trouble code on screen. Although it didn't tell me exactly what the code meant, a quick Google Search found the answer, "Missing or loose fuel cap." Replacing the cap and driving a bit farther cleared the code without an expensive trip to my mechanic.