I've seen a few references in these forums to a "wideband analyser". I must admit that I'm not 100% sure what that actually is. Are we talking about a portable exhaust gas analyser like one of these:

http://www.etoolcart.com/gunson-gastester-portable-exhaust-gas-analyzer.aspx



Or are we talking about an air/fuel ratio meter/gauge like the stuff shown here:

http://www.innovatemotorsports.com/



Or:


I've got to say that the Innovate gear looks pretty neat.

I have one from techedge. 2J1 but I believe there is a new model.
Depends what you want ie one that datalogs or just a readout