I just bought this setup but it was the Kiwi Bluetooth version and an android powered phone running Torque (~$5US, pretty cheap for the power the app has). Look into other apps in the iPhone market as I think there were about 4 or 5 on the kiwi website but for different platforms.
The logging in Torque is pretty cool for monitoring vehicle stats on trips or at the track with a OTA upload as an excel file. I think I even saw other software for track map overlays that when coupled with the GPS, OBDII Data and accelerometer in your phone/kiwi gives you a buttload of track data as you do lap after lap.
For android users:
Torque — OBD2 Performance and Diagnostics for your Vehicle
The wireless OBDII connector:
PLX Kiwi Bluetooth Buy Now- Connect your Droid mobile device to your car's OBD2 OBDII Port
There should be some settings for interval/smoothing for RPM and other 'fast' data (like g-meter). Have you noticed any cool, unexpected PID's for the Z? I've only used mine on our WRX (picking up my Z on Friday).