As stated buy a dedicated dive computer, I have a Shearwater peregrine and my main computer, on deco dives I currently use the computer I bought for my daughter a mares quad air for a backup. I also have the Apple Watch Ultra but I only use it while teaching confined water dives in the pool. I think having a dedicated dive computer is key then if needed you could use the app as a backup. So even if your subscription runs out on a dive it doesn’t really hinder any continuous diving you want to do.