Usually not — but opening the app is not the thing to watch. ROOK can only deliver data that has already been synced. For API-based sources, the wearable has to reach the vendor's cloud; for mobile sources, the data has to reach the phone's health store. Whether that happens on its own, or only when someone opens the vendor's app, depends on the vendor, the phone's operating system and the user's settings.
What has to happen before ROOK can deliver data?
Data passes through three stages, and each one has to complete before the next can start:
The wearable syncs. Either to the vendor's app and cloud, or to the phone's health store. This stage is outside ROOK.
ROOK extracts. From the vendor's API on a schedule, or from the phone through a ROOK SDK running in the background. See How often does ROOK extract and deliver data? for the timing of each source and data structure.
ROOK delivers to your Data Webhook.
Nothing in stages 2 and 3 needs the user to do anything. Stage 1 is where the answer to this question lives.
Does the user have to open the vendor's app?
It depends on the vendor, and often on the specific metric.
Most vendor apps can sync in the background when Bluetooth is on, permissions are granted and the phone allows it. But background sync is best-effort rather than guaranteed, and several things interfere with it: battery optimization on Android, Background App Refresh on iOS, force-closing the app, and the vendor's own choices about which data syncs automatically. On some devices, recorded activities sync on their own while all-day metrics such as steps and heart rate wait until the app is opened.
ROOK cannot control or change any of this — it happens before ROOK is involved. What it means in practice is that opening the vendor's app and syncing is the reliable way to make sure the data is there, even when it often happens without it.
Does my own app have to be open?
No. For Apple Health, Health Connect and Samsung Health, the ROOK SDK extracts in the background and does not need to be in the foreground.
But the SDK reads the phone's health store, so the same condition applies one level down: if a third-party wearable has not written its data into that health store, the SDK has nothing to read. Data the phone itself records, such as steps from an iPhone or an Apple Watch, is already there.
What should I tell my users?
Four things:
Grant the permissions. ROOK can only extract what the user has authorized.
Keep the vendor's app installed and signed in. If a user stops using it for a long time, the connection or the authorization can lapse depending on the vendor and their settings.
Sync regularly. The fresher the sync, the fresher the data you receive.
Don't force-close the vendor's app, and don't put it under aggressive battery restrictions. Both stop background syncing.
Data is missing for a user. Where do I start?
Check whether the user has synced. Missing data is far more often a sync that never happened than a delivery that failed — and it is the one stage neither you nor ROOK can see from the outside.
This is also what governs how much history ROOK can pull at the moment of connection. See How much historical data does ROOK retrieve when a user connects?.