I've bought it, but I havent't used it yet, so I can't speak for how good it actually is. As it's half price atm, I couldn't say no.
From the Android version -
Hema Explorer is available for the special Father's Day price of $24.99 until 14/09/14.
The interactive GPS navigation app for touring, four-wheel driving and camping
Hema Explorer combines reliable Hema maps with 40,000 interactive points and online features to empower touring, 4WD and camping adventures like never before.
FREE Fraser Island, Victorian High Country, Cape York, Kimberley and complete Great Desert Tracks series maps included for a limited time
Hema Topo 1:250K and 1:1 Million Road Australia-wide maps available for free in-app download
Access Australia-wide street, terrain and satellite mapping online
Create routes to clip and save street, terrain or satellite mapping for offline use
Access a map-overlaid rain radar online
100,000+ searchable placenames
Supposedly good maps but Play Store reviews are scary. :|
I use my Garmin Zumo's topo maps for now.