The o2 reading is basically the same as the A/F ratio. However you're probably running a narrowband o2 sensor, so it's not going to help too much anyway.
Knock is the most important part about this device, as it's the most detrimental to our engines.
These are called pocketloggers for a reason. They log info on the car so we can determine what may be wrong with it. It's not gonna flash any pretty lights or tune anything for you... that's up to you. But if you're getting lots of knock, that means something's not right and you should probably try to figure it out.
Here's a link to all the features and what their uses are:
http://www.pocketlogger.com/index.ph...arams&type=dsm