Yes, I've got the Kiwi ODBII WiFI dongle and i use Rev occasionally as well as Fuzzycodes too.
Its a good app, does some simple logging and displays various gauges, like speedo/rpm/maf rate/timing/intake temps. It also does check lights and check light reset from the iPhone
It doesn't replace VAGCOM however, the sample rate is a lot slower than it would be over a proper cable.
However its more of a handy portable tool to use without hooking up a laptop, fits in a phone holder or dock and is easily viewed while driving. The drawback is the cost of the wifi dongle which is quite expensive.