After going through 2 different units using Oziexplorer, I put a Kenwood head unit in with Android Auto. This is the new version of mine.(superceeded) http://www.kenwood.com/au/car/visual_navigation/ddx9018dabs/
It is awesome.
It runs reverse camera and caravan camera.
Hands free navigation, phone, messaging, music etc, etc via Android Auto.
Dont need a tablet for offroad mapping, I use my Android phone via mirrorlink. It is fully interactive (menu, zoom, select etc etc via the Kenwood head units touch screen).
You can run Wikicamps or anything you want via mirror link.
I run Locus maps for off road mapping and it is the best.
Heres why I say that.
It costs around $12 and you can load it on 2 devices for that price.
Excellent glitch free operation.
Easy to use app. Menu is simple even for me.
Offline navigation available via free app add on.
http://www.locusmap.eu/locus-map-can-navigate-offline/
Big online world wide support forum.
You get 3 maps for that price (which is 3 states). Maps are very detailed. Buying extra maps is very cheap. There are android forums where you can get maps for free.
https://www.openandromaps.org/en/downloads/countrys-and-regions
You can add your own maps. Plenty of support via forum.
The feature that Ive come to love the most (beside working so well) is its link to Google Drive. I use Google Earth alot on my PC to find, plan and mark camp sites, overnight stays etc. I upload everything to Google Drive and then download it Locus Maps. Done in seconds. You can also upload from Locus to Google Drive. I edit and add on my tablets big screen and then transfer to my phone via google drive. Leave way points on Google Drive and everything is backed up if anything goes pear shaped on your phone.
You can easily edit your unloaded waypoint icons, names etc individually or in groups.
Once you try it you will be sold.
Heres a few shots of the Kenwood.
Cheers Glen