Both return scores. Sahha returns them without a wearable.

Not at the door, and yes in practice. Both entry tiers list at $399 a month, though Sahha Starter covers 1,000 active users against ROOK Core’s 750, and drops to $299 on an annual plan. The difference is what that price includes: ROOK bills ROOKScore at $249, granular data at $249 and notification webhooks at $99 on top of Core, while Sahha Starter carries every score, biomarker, archetype, tag and insight. Core+ at $999 for 5,000 users bundles three add-ons of your choice, which is the fairest comparison point above 750 users. All of ROOK’s figures are from their own published price list.

Their data-source documentation states there is no phone-only path: every source is a wearable, a health platform, or an app feeding one. They read Apple Health and Health Connect, so phone-sourced metrics can arrive that way, but a user who owns nothing to connect produces no scored profile. Sahha computes sleep, activity and mental wellbeing from phone signal alone. Given wearable ownership runs 13% to 46% across surveyed markets against 82% to 97% for smartphones, that gap is most of a general-population user base.

No methodology paper, validation study or peer-reviewed citation for ROOKScore appears on their site or documentation as of July 2026. Their documentation does state that weights are configurable per client, which means a score is comparable within your deployment rather than against any external benchmark. That is a reasonable design choice for a configurable product, and it is a different thing from a validated one. Sahha publishes the research behind its models, and the models are identical on every deployment.

Their marketing says 400+ wearables and health data sources. Their documentation names 71 distinct sources: 8 direct cloud APIs, 4 platform SDKs, 2 indirect, and 59 apps reached because those apps write into Apple Health or Health Connect. Both numbers are theirs and both are defensible depending on what you count. The honest comparison in either direction is by the specific sources you need, not by headline number.

It depends entirely on whether your product shows history at signup. Seven days for API sources and 29 for mobile SDK sources, disabled by default in production, means a new user sees roughly a week of data on day one. If your onboarding depends on a populated trend chart, that is short. If your product only starts being useful after a few weeks of its own data, it does not matter. Worth knowing in both directions: backfill windows are capped everywhere, Sahha included, and the cap only bounds what gets pulled automatically at signup rather than what you can load in yourself.

It depends on who registered each provider connection, not on the switch itself. ROOK requires you to create your own developer accounts with Dexcom, Samsung Health, Strava and WHOOP, and Sahha runs on developer accounts you own as well, so connections you already hold carry over and those users do nothing. Where ROOK registered the connection under its own account, those users approve once more, into an account that is then yours. Phone permissions are unaffected either way, because Apple Health and Health Connect grant to your app rather than to the code inside it.