Pebble has released a developer preview in which small JavaScript plugins running on a phone provide data and actions to watch apps. The design lets an interface stay the same when its weather provider changes, or lets lighting controls and task creation be reused across multiple apps. Examples can be tested by enabling an experimental option in mobile app version 1.14.0 or later, but it is off by default. The developer documentation says the API is unstable and instructs developers not to release plugin-using apps in the store yet. Each watchface also needs integration work for the new interface.