This is what I'm looking to do. Plan the route on my desktop computer at home, save the route and sync to my phone and tablet. When on the trail, follow the route using Dual GPS receiver using phone or tablet when no wifi or cell service is available. Keep a library of routes so I can reload them in the future or share with others.
For me, this question began with the issue of no wifi or cell service on the trail, therefore no way of navigating in real time. The Dual GPS receiver solved one problem: access to GPS location when no wifi or cell tower in range. Next problem, navigation software that receives GPS information from the Dual GPS receiver so I can navigate in real time on the trail using mobile device.
This thread has been very helpful in sorting out mobile device software to solve real time trail navigation on trail.