Wide band air/fuel ratio gauges?

I had an older cyberdyne afr gauge, yet I didn't feel like it was accurate enough. I don't know how the newer stuff is. One thing I strongly suggest is learing how to read plugs. This can tell you not only fuel ratio, but timing and heat range as well.
Combine reading plugs with perhaps an AFR gauge and you'd have a pretty darn precise idea of what's going on in the engine.

http://www.dragstuff.com/techarticles/plug-pictures.html
http://www.4secondsflat.com/Spark_plug_reading.html