I have a Withings sleep sensor. They recently sent me a marketing mail, based on my previous night’s sleep, with a pitch to improve my sleep through a paid program. I had already opted out of marketing emails so their unsubscribe link had nothing to unsubscribe from.

Is anyone doing scales, sleep sensors, and BP cuffs that don’t use the cloud at all?

If you have an Android phone you can use Gadgetbridge which is an alternative app to sync your smart devices. It keeps all data on your phone. They support lots of devices, I use it with my Garmin smartwatch and I'm a happy user.

Haven't tried it yet but there's OpenMuse for the Athena S Muse headband.

I think there's an open source Whoop firmware now for that.