Unfortunately that's the price you pay to use most devices - they need accompanying proprietary software. There doesn't seem to be a big enough market for open-standard or open-protocol health/fitness tracking.
But... it doesn't. I can look down at my old, not-phone-connected fitbit any time I want and see how many steps I've walked so far during the day. Or what my heart rate it. Or any number of other things.
It doesn't _need_ the phone to be able to do that part of it's job. And I don't want the "challenge your friends to a walk-a-thon" junk that does use the app.
There is a semi-open standard and protocol for fitness tracking: the FIT file format and ANT+ for wireless networking. However most devices which support those standards like Garmin generally require the use of a proprietary mobile app for initial setup. Once you finish that you can uninstall the app.
