This paper describes a technological development project in charge of collecting and relaying data using UAVs (Unmanned Aerial Vehicles) from one or more small, low power, modular sensor nodes that can be placed in remote areas or floating on the water surface. The overall characteristics and architecture of the proposed sensor nodes and system around them are described. Field tests for one custom-built hardware prototype were carried out and the results are presented and discussed. The tests included: a proof-of-concept sensor node in water, an X-8 UAV for gathering and relaying the data and a base station connected to a computer used as an endpoint for the sensor data. The system was created using a combination of standardized and custom tailored communication protocols, firmware and application software. The experiments concluded with data successfully being relayed from the remote sensor floating in water to a UAV and further on to a base station that can be located at tens of kilometers away from the UAV.