One of the major challenges in contemporary agriculture is the precise management of irrigation water, closely tied to an accurate estimation of crop water status. Currently, the available methods for accomplishing this task are time-consuming, non-scalable to large areas, and incapable of providing real-time information to farmers. In this sense, the incorporation of remote sensing tools for the assessment of plant water status is of great importance. One of these tools is canopy-air temperature difference, which is a valuable tool for assessing plant water status given that it provides quick, non-invasive insights into plant condition. This method is cost-effective, scalable, and suitable for various crop types, aiding in efficient irrigation management, stress detection, and optimizing agricultural practices. Consequently, this research aims to design a low-cost, spatialized-capable device based in the canopy-air temperature difference for predicting the water status of lettuce crops in greenhouse environments. The development of this device considered the ensemble of the device, where a series of components were integrated into a low-cost sensor. Afterwards, laboratory tests were carried out to assess the precision of the sensors. Finally, a test was carried out under greenhouse conditions, where the performance of the sensor was tested under real operation conditions, allowing to calculate the canopy-air temperature difference in order to assess an estimate of lettuce water status. The results of this study indicate that this device will generate a tool that can be used by farmers of any scale, ultimately enabling efficient management of water resources.