Hiya. I have a pre-release Pebble app called “Fit Tracker” that tracks running/biking workouts and creates FIT files that can be uploaded to Strava. The Pebble Companion app is used for the GPS, and the FIT file has location, time, pace, and heartrate information.
The Strava developer portal allows for NINE more testers if anyone is willing to try it out. Here is the link (the app is hidden in the Pebble App Store)
The instructions are a bit wonky unfortunately. You will need to add your Pebble serial number at https://fit.setpebble.com, and then use this serial number when modifying the Fit Tracker settings in the companion app. After a workout, do a long press on the up button and choose to save your activity. You should then be able to see your activity in your https://fit.setpebble.com account where the map is shown, and the FIT file can either be downloaded or uploaded to Strava.
Someday my ancient web site (https://setpebble.com) will be replaced by the modern https://fit.setpebble.com interface, but that is a future project.