I had the Plx Kiwi Wifi and Rev for a while (I recently sold the Plx tho).

They are a great combination if you have a newer OBD car, Rev uses the iphone's accelerometers and can plot a track if you are driving one, showing you acceleration, braking and corners.

Also great for cool looking gauges (like boost, EGT etc), and has the ability to datalog and graph the information too. About a month ago the upgrade to Rev2 came out, which is nicer looking, but also shows calculated Torque and Horsepower figures .

It's a nice bit of kit to have for both the novelty, but also the function, I've cleared a few mates Check Engine Lights now with it

Sold it in the end as I wasn't using it all that often (still have the app on my phone, but not the Plx OBD plug in), and was thinking of buying a genuine VAGCOM lead instead.