Remember a post from someone deep in the bowels of BOM a while back. Lots of expense on AWOS installations. BaroVNAV was to be Australia's answer for our commitment to ICAO re-availability of GNSS based approaches.
Dick, could it be the Garmin gear has the capability although I fear you need a FMS to drive the approach and only those approaches depicted with a TWR or AWOS for a current BARO setting?