I tried my hand at creating a Garmin datafield app. It was so easy I created two of them. One a MET (Metabolic equivalent of Task) display, and the other air oxygen concentration display for mountain climbers, and people exercising at higher altitudes. Although not the first of each of these in the Garmin store, both of them have unique features not available in existing datafields in the store that display MET and O2. Check them out here:
MET Datafield: https://apps.garmin.com/en-US/apps/d487afae-e747-4cbc-ab3b-87f447a21234
OxyCon Datafield: https://apps.garmin.com/en-US/apps/aa6c4573-7066-4e37-b73f-d2ac4d6364c0
