I've added a remote sensor using an ESP8266 and a MSP430G2553. The sensor is currently configured to detect the presence of water and send and alert to the web server if it does. The new code(and modifications to web page files) has been posted on my GitHub repo here.

A little backstory: I've suffered in the past from water leaks from the washing machine, the last leak damaged my flooring in the hallway.

I of course plan to do more things than just detect water with remote sensors in the future. The downside of using the ESP8266 is that it's a power hog, which reduces the practicality of making the remote sensor battery-powered and thus limits where I can place it.