Guys, I was originally after something just to show me trouble codes.
Then I found I had a bit of real estate on my dash that needed filling with something.
So I got the scangauge:
ScanGauge - Trip Computer + Digitial Gauges + ScanTools
It shows all trouble codes and can also turn those codes off.
Does a whole heap of other stuff as well which may be handy if you want trip gauges /fuel consumption/alarms etc.
There is a cheaper unit called a Ultra Gauge which does the same thing.
UltraGauge OBDII Scan tool & Information Center
Both units just plug into the OBD11 port.
Scan Gauge is a bit expensive but enjoys an excellent rep.