The information might be on the obd bus, but that is a long way from getting a scangauge to display it, unless you are ron delong, or his latest version allows you to display any pid you want. Any open source obd scanner software could be adapted to display it (again, assuming it is available on your car)
$19F4 Gear box ratio
$19F5 Current gear
http://www.obdproject.com/OBD2Info/Specs/pidlist.htm