I've used my droid for a couple of years to aid navigation, but your app appears to answer some needs. I downloaded it last night and put in a test route from myplaces and watched myself go to work.
You mentioned cache ing maps prior to entering areas w/o reception. I too ride the NC mountains and I frequently lose my navigator function. Are you referring to adding the myplaces maps to layers or to what other function are you referring? As you can tell, I'm a noob at this.
'06 DR650 - Suzuki
'95 750 Nighthawk - Honda
'83 650 Nighthawk - Honda
'71 SL 350 - Honda