I bought a bluetooth dongle for £5 (ELM 327 mini) which plugs into the OBD port. It will link to a bluetooth enabled laptop or an android tablet in my case, or even a smartphone.
A free app called 'Torque' allows you to interrogate fault codes, reset them (if the EMU allows this) check things like coolant temperature and power output etc. etc in real time or plot them on a graph. It also, if your phone/tablet has gps, allows you to plot the course of a journey on a map with the colour of the trace indicating the coolant temperature or the position of your foot on the gas and lots of other things.
It is a lot cheaper and a lot more flexible than a scanner if you have a smartphone. See it in use on you tube here for instance
http://www.youtube.com/watch?v=vQSsUPrGLHs Torque pro costs a couple of pounds more than free torque but its well worth it.
I really wouldn't mess about with a dedicated scanner.