Go over to one of the Tweecer sites and see what wb's those guys are using. Over the last several years they have really come down in price. I use a FJO but it is several years old and it has been upgraded several times since I got mine.
Not sure but I think you can have several options in the 250 to 350 dollar range.
I would personally just buy the TweecerRT...its more expensive but you can do the same as that and a whole lot more...TweecerRT will run you about 550 i think...but its worth it.
I've got the PLX M-300 and love it. That zeitronics one looks fine, but I think that it may be difficult to glance at it to see the current A/F ratio while driving. The PLX unit has a much larger, simpler display. It doesn't do the datalogging or have all the extra inputs, but with my TwEECer RT, that doesn't matter.