Here is a nice overview of Wide Band Oxygen Sensor (WBO2) electronics.

http://www.tragacs.com/wbo2.html

A pal used to sell the parts & circuit board kits, just as a service to the Do-It-Yourself Electronic Fuel Injection (DIY-EFI) list subscribers. TechEdge ripped off the design and is selling the electronics at substantial profit.

Here is a link to the DIY-EFI "non-profit" WBO2 kit site:

http://www.diy-wb.com/info.htm