As I said, I think all GT31s have speed genie, hasn't yours got it?
As far as I remember, the difference is whether the speed genie shows the best runs for the session as well as the last runs. The early versions only showed last run.
If you PM me with your email I can send you the latest version, but you'll need to find a mate with windoze
Although saying that, this page has a mac driver for the GT31.
www.locosystech.com/en/product/Genie-GT-31-BGT-31/gps-handheld-data-logger-gt-31.htmlAnd also version 1.4
The one I have is V1.4B0803T