The Simple Pedometer 4+

The simplest, nontrivial, noninvasive, light *footprint* (get it?) pedometer app for iPhones (5s or later with built-in motion co-processors).

Features:
• no registration or internet access required (privacy). Only contact with server is to check for updates.
• basic app functionality is free with no advertising
• lightweight: app size is < 1MB
• no active resource usage (unless you explicitly enable and start run tracking): basic step-counting does not use battery-draining GPS, or use push notifications: updated only when you want it to update.
• does not run in the background (unless you enable badge displays... which are updated at a schedule set by iOS); you can even kill the app - as long as it is run at least once a week (the limit of the iPhone's onboard internal history) your daily step count will be queried from the phone and logged to the step history.
• stopwatch mode: start and stop tracking your steps within a time interval on demand
• graph your step history by rotating to landscape mode
• pan step history graph to view different date ranges
• challenge yourself by tracking your moving average number of steps
• long press and then drag to select a range and display the cumulative step count
• triple-tap a step count bar in landscape mode to make manual changes to the step count for previous days.
• simple light and dark themes
• Enable run/hike mapping with GPS assist to plot your route and produce essential statistics... unlock the 'Run Archiving and 3D Display' feature discussed below (now free!) to persist your runs across launches and add a vertical dimension to your data... as far as I know, this is the first app to offer this.

The two advanced features that were formerly in-app purchases available allow you to:

• save/archive your GPS-assisted runs/hikes (grouped into monthly runs) in a highly compressed format for future reference, and (unique to Simple Pedometer as of this writing), present your run/walk/hike data in an elegant 3D view so as to annotate significant altitude changes (gains). In 3D view you can display the individual speed, distance, altitude coordinates of your run or hike, and see your net approximate elevation gain; also unlocks unlimited run/hike mapping;
• annotate your step history with comments, and export your data via e-mail as a simple comma-delimited text file.

Please note: Continued use of GPS running in the background can dramatically decrease battery life. (In my testing on an iPhone SE and 7, about 3-5% per hour running in the background.)