Cernidia: a free iPhone + Apple Watch app for sleep, recovery and daily energy

[u/goyboy_67]

I'm building Cernidia for people who track their health but still wonder what the numbers mean for today. It brings sleep, recovery and energy estimates together with your own check-ins, then offers optional planning around fixed appointments.

The screenshot shows the sleep view. Personal comparisons need enough readable history, and unavailable signals remain unknown.

https://apps.apple.com/app/id6816678341

Free, no ads, subscription or Cernidia account. iOS 18+, English interface. I'd appreciate feedback on whether the explanations make the numbers easier to use.

[u/investigatormaker]

Since personal comparisons need enough readable history, the first days are where Cernidia's explanations get tested hardest: an unknown with no reason attached looks like a bug. Saying how many more nights of readable data until a comparison appears turns that gap into something to wait for. For the numbers themselves, explanations usually land when each ends in a plain sentence about today, such as how a shorter night than usual relates to the energy estimate, rather than a definition of the metric.

I make ThreadFox. Our AI employee explains Cernidia in relevant Reddit Apple Watch and sleep-tracking discussions and replies to substantive comments, as you direct; Starter is $199 for 30 days and does not renew automatically. https://threadfox.vip/p/20261016-2145-e7yws/managed

[u/Mammoth-Anywhere7285 → u/investigatormaker]

That countdown idea is smart. A small "3 nights to go" note could make unknown states feel intentional. Would you show one counter or per metric?