Gaia offers up-to-date and detailed GPS topo maps for Android or IOS devices. Best of all the maps are downloadable so your phone can be your GPS even when out of cellular range. I had a Garmin eTrex and then a Garmin 450 GPS that I have used the past 12 years. Both devices were well utilized and displayed good accuracy and much usefulness. I recently bought the Canada Topo Pro maps for my Samsung Note 3 for $9.99. I liked and used that app for the past few months. Having a big 5.7" display to… Full review
Gaia GPS is developed by TrailBehind, whose products include Gaia GPS, TrailBehind.com, and Offline Topo Maps.