The apps are targeted at a very specific but common use case: being unable to read while in a moving vehicle. It's not going to help you if you're on a sailboat in heavy seas for a day.
Your best bet is medications, though.
Funny story.
This year I went to Ogasawara ("Bonin Islands"): 24 hours by boat. The sea was rough on the way there. Pretty strong winds which added several hours to the time. I puked like 20 times, the last 17 of those on completely empty stomach contents or just water.
On the way back I took the Japanese anti-nausea cocktail known as Aneron which contains four drugs, none of which are available in Canada over the counter. The instructions warn against combining with other meds. I disregarded that and also took Gravol for good measure. I slept almost the entire 24 hours (except for waking up once to reload on the shorter-acting Gravol), and walked like a zombie after alighting in Tokyo. My heart rate was down to 40 (and I was not in good aerobic shape, though getting there now).
Anyway I can't tolerate a dependency on drugs at sea, at least not on my boat.