There are some pricey units available from various vendors, Ramchargers has a stand alone wide band O2 for $1100.
If you are handy you can build one apparently. I haven't tried it, but this is what Bruce Plecan posted to the GN T-type list:
Date: Wed, 22 Nov 2000 13:11:46 -0500
From: "Bruce" <nacelp@bright.net>
Subject: Re: DIY WB
Seems like some folks may have missed this,
a DIY Wide Band O2 (not to be confused with an oem switching type).
anyway, please read the users agreement, and either abide by it or pass on
the whole thing. It's to guarantee that work continues on other projects,
if folks won't abide by it, that will kill off other projects. It's meant
to be educational, ie if you don't know how to solder this would be a great
time to learn, selling assembled boards, for profit does violate the users
agreement. It's written in clear english, let's not mess up a good thing
here, OK?.
It's not meant to be a lab grade unit, and so far the display is limited to
using a DVM, thou there is a bargraph design floating around. I've
compared mine to several others, and commercial units, and they are close.
Remember you never tune to get a specific AFR, you tune for best
performance. It as well as EGT are only tuning aids!. Reading plugs is
still necessary. No it won't directly interface with a ecm of any sort.
And again the display so far is limited to a Digitial Volt Meter. There is
a voltage to AFR conversion, included.
1st address is for basic information,
the second for the printed circuit boars
the 3rd for the parts kit (all but misc wires, and sensor)
(NAPA generally has the best price on the sensors).
http://www.diy-efi.org/diy_efi/projects/diy_wb/
http://208.37.117.207/wborder.html
diywb@ciciora.com.
The GP for the boards is currently shipping ones from the last batch, and
I'm not sure how many parts kits are left.
All of the people working on this are doing all the work for free, so your
not paying for instant replies, and daily updates. If you order a board,
you'll get the price after the GP closes, the prices vary by number ordered,
so the exact figure may take a few weeks (month) to be finalised. Same with
the parts kits. Being absolutely non profit makes it easily affordable, but
the down side is no one is working full time answering *me-too* guestions.
Also, if you order once, don't repeat your order, unless you want another
board. You'll get it when things are shipped, after your check is recived,
oh, and no checks are cashed till stuff is shipped (current policy).
There has never been a net project like this before, where everything is
non profit, and folks tend to confuse it with commercial items which are
totally different. This has been in the works for 4 years. Alot of time,
and money went into bringing this to life, please don't get into work games,
and wanting to cash in on it. While we have to pay for the boards, and
parts, the folks we buy them from make some profit on it, but noone on our
end is making a penny.
This is not a commercial advertisement, again note it's non-for-profit.
Just a random act of kindness.
Hopefully, Santa is on the look out for something else <g>.
There is an ongoing discusion about it on the DIY, but all the tech stuff
is in the archives, if you want to get all the details. In the not too
distant future there will be a web site devoted entirely to this.
If there is enough interest maybe, we could expond upon it here (ie
mountings, etc).
Bruce