Change-detection monitoring plays a crucial role in geoscience, facilitating the examination of earth surface processes and the mitigation of potential risks due to natural hazards. A significant aspect of this monitoring involves the use of images, enabling 2D to 4D monitoring approaches. Our objective is to bridge the knowledge gap in developing very low-cost camera units by providing insights into specific products, assembly processes, and utilized codes. The presented approach involves prioritizing cost reduction albeit a trade-off in system quality. The results obtained in the study area of Puigcercós cliff in Spain demonstrates the system's efficacy in detecting rockfalls and pre-failure deformation with a notable level of detection of only 8 cm in the change detection analysis. Additionally, two system versions are presented; one emphasizing real-time image transmission, while the other provides a simpler, energy-efficient approach conducive to long-term data capture using a single battery. Both solutions showcase the potential of leveraging very low-cost technology in geohazard monitoring.