Hi mate, I've done a bit of research just recently on these too.
I looked at the Zietronics ZT-2, PLX Devices (various), Dynojet, LM-1 and Haltech units. There are loads more too.
Bloody minefield of different options and features.
The ones I looked at were all data loggers too which come with various software, so they offer a bit more than stand alone wideband O2.
Be very careful as some units are utter bollocks without being able to be accurately calibrated and hence returning pointless afr's etc.
I bought an R500 from plx devices. Its seems a bit pricey but not too bad when you consider that it comes with an EGT + Wideband O2 sensors, full data logging of practically all ECU data, knock, tps, wideband o2 (convertable to narrow band for ecu and gauge output and linkable to any aftermarket ecu), egt, engine load, etc etc, seems a good bit of kit, lots of race teams use it so quite reassuring.
It should arrive shortly so i'll do a post to show how i've found it.