Hey Paul,
Check these out:
http://www.speedohealer.com/eng/intro.htm
"SpeedoHealer v3.0 - just released!
with 3 functions in 1 unit!
Programmable Calibrator
Calibrate your vehicle's factory speedo and odometer to get 100% accurate readings
Make sprocket conversions road legal by speedo re-calibration (in certain countries)
Converter
Convert miles to kilometers and vice versa on import vehicles
Set your speedo reading according to the local standard during your trip abroad (e.g. to/from the UK)
Advanced Top Speed Memory
Recall your true top speed to your factory speedometer by press of a button"
They have harnesses to plug into the RC as well
Because I'm so nice, I found all the dealers in Australia for you:
http://www.motofx.com.au/listDealers.php