After trying several GPS driving programs, I have settled on TomTom. I just completed a two day drive to ski in Colorado that covered 900 miles. My iPad was mounted in the center dash compartment with a minor modification. I used the GPS function for route info since I tried a new way of traveling. Since driving in Colorado is lousy for radio reception, I found a cable that would connect to the radio's input jack and had a USB plug for charging and played music from the iPad tunes. One of my GPS programs provided elevation readings through the mountains. Finally, I used Gas Buddy to plan the best places to get fuel.
My only problem was that the GPS programs are battery drains. No matter which charger I used, it would still drain. With the 2amp chargers, I went all day without going below 40%, but if we had done one of our 15 hour non-stop runs, we would have turned the GPS for periods to recharge. We also used the TomTom to find places to eat and Wal-Marts for rest breaks on the route.