Final Project for CS50: https://courses.edx.org/courses/course-v1:HarvardX+CS50+X/
The ESP8266 runs a program once every hour that takes a soil moisture reading from a houseplant, provides visual feedback via OLED display and sends reading over WiFi to server which then updates a MySQL database via PHP. If the houseplant is found to be "dry," an email message is sent via PHP to the user.
WeMos D1 Mini (ESP8266) with WeMos-made 64x48-pixel OLED Shield and YL-69/YL-38 soil moisture sensor.ESP8266 code tested and compiled via Arduino IDE 1.5.4. The server requires MySQL to store soil moisture values. The website itself is designed MVC-style, using CS50's Problem Set 7 as a basis (without utilizing the CS50 Library), and utilizes the Bootstrap framework, Google Fonts and CSS3 for styling.
Though the WeMos D1 Mini goes into deepsleep, eletrolysis is likely to erode the sensors of the YL-69 over extended use (a week or two).