I just checked our Scangauge and it doesn't have the X-Gauge function. To check yours, push the button with the red ring and then More>More>More. If you have the X-gauge function, it will show on this screen. If not, it will show "Use Defaults" and Version (if I recall from viewing a minute ago).
Here is the information on upgrades:
Unfortunately, while ours is a Scangauge II, it was purchased back in 2006. But $25 is a lot cheaper than having a transmission temperature gauge installed! Thanks Scatter for bringing this to our attention!