Boating Suite ($5 on Apple) has a wide range of nonnavigational features and a nimble interface;
AyeTides ($10 on Apple)
MyWeather (free on Apple and Android);
myLite Flashlight (free on Apple)
My Tracks, from Google (free)
Tide Prediction (free on Android)
Of course, one low tech tip is in the article which I use and heartily recommend—And if there’s foul weather? Easy. Slip your phone or tablet into a zippered plastic bag. It’ll still respond to your touch, and if it goes overboard and there’s some air in the bag, it may even float long enough for you to rescue it.