An ESP8266 based project to monitor the flow of water (or any fluid, for that matter) in a pipe using a flow sensor. Also Android app to display the info
The firmware is a mess, but it works.
The app is incredibly low effort too. The IP address for the ESP8266 is hard coded.
The above is the app
I used an ESP8266-01 for this, but you're welcome to use some other model, of you wish. You will have to edit interrupt_functions.h file to accomplish this.