It sounds like you are describing a Garmin watch. It uses an app to sync with Apple health but will happily run offline for a week until you can sync it. Ther

It sounds like you are describing a Garmin watch. It uses an app to sync with Apple health but will happily run offline for a week until you can sync it. There are also heart rate bands you wear around their chests since you mention non-watches. I am not sure if those will work without another device to sync with though.