Portable Air/Fuel gauge?

I don't know if this has ever been asked before, but does anybody make a portable wideband air/fuel meter that doesn't require welding in a bung for an O2 sensor? - Possibly with an O2 sensor probe that can be inserted into a tail pipe with a handheld meter and can be moved vehicle to vehicle? Is it possible? Or do the sensors have to be located further upstream in the exhaust to work correctly? I would like to be able to use one for tuning without having to modify (drill & weld) the exhaust if possible.