To download TTMaps go to
ttMaps
TTMaps uses ECW formats which you can download maps from
Maps of Australia - Geoscience Australia which are 250,000:1 which is ok when driving long distances. You would need 25,000:1 or better to be useful. The good thing you can swap maps on the fly by zooming. I used the 250,000:1 for road trips and 25,000:1 when on location. I live near Algester/Calamvale and can show you it working. The next GPS will be able to run OziExplorer CE.
Some useful links.
Maps and GPS Info