This application is designed to be used with the Eyegas sensor. The Eyegas application can measure the LPG propane level to tell you the exact fill level and when your tank is empty. It can be used on tanks found in RVs, heaters, BBQ grills, etc. The Eyegas sensors are magnetically stuck to the bottom of your propane tank and will periodically measure and wirelessly send the fill level or percentage to the Tank Check app. Stick it on the bottom of your tank and know exactly when you are running low on propane! This technology is patent pending.