Remote monitoring of propane tank fuel levels can have many convenience and cost benefits for both suppliers and consumers. For suppliers, physical tank checks can be eliminated while reducing the maintenance and fuel costs for fill trucks. As a result, customer satisfaction can be increased according to better visibility and quicker service. For consumers, monitoring eliminates physical gauge checking, offers a better understanding of usage habits, and eliminates running tanks dry for remote or part-time residences. The current monitoring devices on the market are expensive and are not designed for a battery life of greater than 5 years for wide-area coverage. The development of an open-source cellular device with secure communications and self-sustaining power is investigated. The Rust programming language is reviewed for its possible use in the prototype for its memory safety and speed. During the development of the monitoring device different communication protocols, micro-controller hardware, sensor hardware, and power sources are compared. The resulting prototype uses a Conexio Stratus development kit based on the nRF9160 system-in-package (SiP). The CoAP protocol is utilized with DTLS over LTE-M networks which offers efficient and secure communications to the cloud with pre-shared keys (PSK). A lithium-ion capacitor (LIC) paired with solar-charging eliminates the need for a battery, which can supply power for the entire life of the device. Power profiling demonstrated the LIC's ability to store enough energy to power the device up to 28 days in the absence of any solar charging and a minimum of 90 % transmission success rate. Sensor testing showed that the hall-effect sensor setup can accurately measure between 10 % and 95 % fuel levels with ±1 % accuracy compared to the gauge position.