Step counts as well as the fitbit. Heart rate is simple. How can it mess that up? Blood pressure is relative. You don't expect it to be accurate without a cuff. Same with O2. Those can show whether you're higher or lower "now" than you were an hour ago, a day ago, but they're not intended to be accurate on an absolute scale. Sleep seems to match up pretty well with snorelabs.

Now that I think about it, I wonder how well any of them keep time without syncing to their app.