I have created iOS shortcuts to use the phone calendar to save events for both. These will save future events called "Change Pod" or "Change Dex". The events are set at 3 days (Pod) or 10 days (Dexcom) to remind you of the next change. The Pod event has an alert 2 hours before it needs changed and the Dexcom event has an alert 24 hours before it needs changed. The shortcuts also create history events called "Pod Changed" or "Dex Changed" so that you can always easily see when they were changed last.
Unfortunately, it isn't possible to delete calendar events without prompting the user every single time. So if you change either of them early, you'll want to delete the existing Change Pod/Change Dex event for the originally scheduled change time.
Click the links below from you iPhone and follow the installation and instructions. You will need to select the calendar to use twice for each one during setup. If you are using this as a caregiver, you can first create an iCloud shared calendar so that others in your family can see the events in one place.
There are several methods to access these quickly and easily.
1. Home Screen Individual widgets.
Add the single shortcut widget. It may not show the Dex/Pod widget when you add it, but that's ok. After adding it and exiting the Home Screen edit mode, long press on the widget and select Edit Widget. You can then change it to the shortcut you want.
2. A Home Screen widget Shortcut Folder.
In the Shortcuts app, add a new folder and then move these 2 shortcuts to the folder. Then on your Home Screen, add the shortcuts folder widget. You may also need to use the Edit Widget option like #1 to select the correct folder.
3. On your widgets screen (left of Home Screen)
Swipe to the left screen and tap the Edit button. Then proceed to add either #1 or #2 in the same way.