https://www.kickstarter.com/projects/82 ... ater-meter
Can this ultrasonic range finder for the Arduino do the trick? $1.80
http://www.aliexpress.com/item/HC-SR04- ... 4,201409_1
Plus a $2 ESP-12. And a $1 wall wart. Still $5 left over.
Theory on how they work.
http://www.engineeringtoolbox.com/ultra ... d_495.html
So when can I read about this amazing ESP hack on hack-a-day?