The Pebble mobile app will attempt to keep your app running as long as your Pebble watchapp is running. However, under certain circumstances, the phone may kill the Pebble app and your app. If this occurs, the Pebble mobile app will be automatically restarted (and your JavaScript code with it).
As Pebble's documentation mentioned here, the official Pebble app could be launched automatically while the connected Pebble watch is running a JS extended app.
My question is that can we also launch a companion app programmatically from Pebble watch? And how? I couldn't find any clues on the developer website.
Note: PebbleKit Android and PebbleKit iOS cannot be used if the Pebble project contains a PebbleKit JS file. Remove any JavaScript files in the Pebble project to ensure communication with Android and iOS companion apps.
According to the documentation here, we can't integrate JS extension together with PebbleKit iOS/Android, that's why it's important to ask this question.
Nope, unfortunately this isn't currently possible. Maybe in the future this will be possible by passing around some deep links.