Wireless Tank Level Monitor

This is a wireless tank level monitor I threw together for monitoring our house rain water tank level which is about 60m up the hill from the house. It runs on a couple of arduino pro mini's and uses a ultrasonic sensor to detect the water level. The components are as "cheap as chips" and is a bit of fun to put together.
It consists of a solar powered transmitter which sits on top of the water tank and senses the water level, then converts it to % full. This is then transmitted to a hand held r