AMPERIT OBD-II Pocket Scanner : JC Whitney: Auto Parts & Accessories
I believe is the unit I have. I'm not sure if the fit has a memory unit attached to its ECU, but all you have to do is connect it before shutting it down and it will tell you what has been going on while you were driving.
As I said its mostly to diagnose problems. I sincerely doubt you are causing enough knock to worry about and also if you are going to be exploring the lean burn regions you will need to re-map your Fuel-air ratios. If and when you do that you will probably have an on-board computer that runs a program to change the fuel maps, but then you can also get programs that read the diagnostic codes. If you straight-up hardwire the map(set it on a computer connect an ECU tuner to the computer and then unplug and connect the tuner to the engine) then you will want one of the above tools to make sure you aren't damaging something.
Honestly I would wait until you have decided you are going to go lean-burn settings and are getting the equipment to do that. Thats where that scary dangerous pre-ignition lair is. As long as you aren't tuning the ECU to inject alot less fuel than normal its not likely to pre-ignite.