As requested I've setup a sticky with some info on OBD scanners, I found this particularly useful for monitoring dpf soot levels.
The OBD port is located below the dash near the drivers right shin. You will need an OBD2 dongle that supports bluetooth or wifi so that your smart phone can connect.
Below is an example of the ELM327 bluetooth dongle I used:
Once this is plugged in and the car is turned on/running you should be able to connect to it with your bluetooth phone (Android), iPhone will need a wifi dongle.
On my Andriod phone I use torqueapp pro from the google store:
With that installed and your phone connected to the dongle you can add gauges, there are some standard ones, or you can add custom ones, like the dpf soot level as below (thanks to Steve1307):
settings > Manage available ODB2 PIDs
"add custom PID"
Short Name: DPF % full
Scale factor: x1
unit type : %
I have had a problem where cycling the car from run to off to start while the torque app is connect triggers a MIL, but no other adverse effects.
Steve1307 has also come up with a list of PIDs that can be used, if you have a JG account, you can download them here:
Please feel free to add to this thread if you have any other tips.