As I understand it, most of the Pebble’s OS is currently Open Source. Traditionally, you could download updates and applets, watch faces for your Pebble through it’s app, as well has have many phone integrations. Most of the phone integrations can now be done through GadgetBridge and applets downloaded from Rebble.
Given the minimal need for always-online or really much of a internet connection at all beyond what is needed for third-party applets (weather watch faces, etc.), the older Pebble smart watches are able to be made about as private as one could reasonably expect from a Bluetooth wearable.
The two upcoming remakes appear to be basing the mobile app and applet repo upon the Rebble community’s work, if not outright using it as the source. If the watches gain GadgetBridge support and/or the companion app is fully open source, I imagine these will be as worthy as the older watches.