Mobile reminder apps do not really serve the purpose because most elders are technology-phobic and most apps are NOT elder-friendly. In fact, in many cases they end up becoming another point of stress.
Constant tending to the App to ensure new reminders are fed, changing settings, reinstalling new versions, adjusting to new version UIs. All of this is too much for the elderly.
Seniors quite frequently tend to push the wrong buttons, some times due to confusion or physical weakness or tremors. Icons tend to get deleted scaring them witless leading to another stressful call for help.