For my closest weather buoy data, I have a bookmark for the noaa web page on my phone's desktop.
Same with one for the noaa marine forcast for my area and one for tides.
also, a bookmark for accuweather since noaa's forcast dosn't mention if its sunny or rainy.
As far as actual apps, i have mx mariner for raster chart gps which works great, but i never really use it in practice.
I have a compass app that i forget the name of that lets you take a bearing by aiming your phone as if you were taking a picture with the camera on it.
I just downloaded marine traffic which lets gives you AIS info with actual pics of the ships. Just in case i'm about to get run down by a supertanker, its nice to know which country it hails from.
Also, apps for sailet and that "other" forum.
Oh and seatow... just in case.