Prius logging with iPhone/iPod

Dear all,
I have been amazed by the data shown by Bob Wilson since my very first visit to this forum (like in http://priuschat.com/forums/gen-iii-2010-prius-fuel-economy/68603-same-prius-not-same-mpg-7.html), and some other people (as in thread http://priuschat.com/forums/gen-iii-2010-prius-fuel-economy/82909-super-highway-mode-shm-hybrid-system-indicator-hsi.html). Now, I want to see for myself what I can get and understand from my Prius (I have to admit I am a geek).

I am looking for a data logging system that my wife will tolerate and my kids will not break. So, I have to rule out a laptop connected to the OBDII port. I came to the conclusion that a Kiwi Wifi device (PLX Kiwi Wifi - Connect your iPhone / iPod Touch to your car's OBD2 OBDII Port.) by PLX devices would be great and the logging "computer" could simply be my iPod that is already an accepted member of our Prius ecosystem. There are two applications on iTunes that allows one to log data from the Kiwi wifi device: Rev and Dashcommand. They are not free, though (49.99$ for Dashcommand and 39.99$ for Rev). My main concern is that Rev does not seem to be able to log more than 5 PIDs at a time (it seems to log only the PIDs it displays) while it is impossible to know how Dashcommand performs on this point. Is there a Prius enthusiast who have tried or have bought Rev or Dahscommand and can comment about that or give its impressions on the logging functionalities of the apps ?