Whilst it can't be used to re adjust the actual speedo, it does have a function to show the speed on the scan gauge, and a function where you can adjust this read-out to account for bigger tyres.
For example:
The 07's came out with 245/75-R16 tyres (roughly 30.5"), I put on 255/75-R17 tyres (roughly 32"), which is an increase of about 5% [(32/30.5)-1]x100
So the speedo on the instruments will read 100km/h, and the scan gauge can read this input, adjust it by +5% and then the scan gauge will show 105km/h
I checked this against a gps and it was spot on
edit: and when adjusting for 285/75-R16 tyres, its close to +8% over stock