Nowadays all available car parameters are monitored (see http://en.wikipedia.org/wiki/OBD-II_PIDs for a detailed description).
Using a bluetooth ELM327 device and our Android mobile or tablet, we can check the car sensor values.
Main window shows speed and RPM. Also, if GPS is present, that window will show current GPS position and GPS-speed.
At the bottom, detailed sensor information is shown (and updated every second).
Compatible ELM327 adaptors can be found at any automobile shop and online webs, i.e. http://s.dealextreme.com/search/elm327
This application stores all data in the SD, in a folder called OBDii_ELM327.