Snapshot Heart Rate (HR) is a simple 1-field data field for the Forerunner 230/235/630/735XT that shows a scrolling heart rate graph of the last ~15 minutes of your activity, colour coded by you profile zones, along with other essential information for your run.
Customisable data options include displaying the timer or distance in the bottom field, and one of time-of-day, battery percentage, average HR, cadence, average cadence or none for each of the top left and right fields. The colour of the background is additionally customisable.
Snapshot Watch can be downloaded to your device here: https://apps.garmin.com/en-US/apps/7f398bbb-43a8-4fc7-a1b0-01c6121ce7d9