Thanks for the tip, Chuck! Based on a friend's recommendation, I've been using Topo Maps + (free, downloadable topo maps you can use offline). Directionality is the tiniest bit off, but about 99% of the way there. I'd be interested in comparing how it stacks up against MotionX-GPS — there are so many navigational apps out there, I only listed Gaia because it appears to be one of the most popular.