SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.
Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Recurrr - Send recurring emails
ioBroker - flexible and modular application for the IoT and Smarthome
FollowUpThen - The simplest way to schedule an email reminder
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation