I’m not sure you’ll find an app that is perfect… just apps that do the job.
I have been using Map My Fitness on my android, to record my miles. They have a section on their website about maximizing battery life. Even following their recommendations, it still wears the battery down faster than I would like… so I got a back-up battery (or portable charger). My wife says its the biggest battery that Walmart carried, and cost a whopping $15.00. Before I go out, I plug my phone into the back-up battery, and set them both together, into a waterproof case. The longest paddle I have done yet, was 10 hours, just over 53 miles. My phone was at 100% when I was done, and my back-up battery, still had 75% battery left, according to its 4 “battery charge remaining lights”.
Although I have not needed it for navigation, I did check my progress when I was getting a little concerned with the daylight I had left… But google maps was easier to use for that. Because of my dis-trust in electronics, I had paper maps that I printed out, and put into plastics sleeves. The paper maps were under my deck lines right in front of me, so I could keep track of my progress that way. In my youth, all I had was paper maps when I was out and about, but the electronics of today are pretty amazing.
Because I have an interest in river current speeds in MPH at different flow rates, with advice from here, I have been using a Garmin Forerunner on my wrist, that shows pretty incredible information on speed, direction, heart rate and the like. Not that its a big deal to me, but this information is “after the fact”, when it is loaded into Garmin Basecamp, so it doesn’t do much for navigation.
Often, when I go out, its just to the local beach, to practice rolling, edging, etc… When I do that, I call my wife to tell her where I’ll be. Usually, I’ll just roll a few times, and then start paddling. Whenever I’m not going to be in one spot, I either call or message my wife to tell her what I’m thinking. Because my plans always change, I also “share my location” (android, google maps, shows a blue dot on your location, tapping on that blue dot brings up an option to share you location with someone.) If anything was to happen to me, she can forward that “link” of my current location to anyone she chooses.
So… the short version… When I’m on the water, 1) I have google maps running, sharing my location. 2) Map my Fitness, tracking what I’m doing. 3) occasionally, I’ll be using a GPS speedometer, showing only my current speed, not a location or map. With a back up battery, I’m never short on battery. If I ever plan to be out for more than 2 days, I’ll have a second back up battery.