Had an email chat with one of my users which resulted in probably the simplest, and yet the most useful, DataField I've ever built... and I still can't work out why it hasn't been done before: https://apps.garmin.com/en-US/apps/191d99c4-374f-4265-94bf-873cb0687d61
(Or, if it has, why I can't find it in the Connect IQ store.)