Communities in Fiji and Tonga rely on landscape services to support a variety of livelihoods. These communities are increasingly vulnerable to climate (e.g. increasing cyclone occurrence and intensity) and environmental (e.g. mining and deforestation) stressors. Within these landscape systems, accurate and timely monitoring of human-climate-environment interactions is important to inform landscape management, land use policies, and climate-smart sustainable development. Data collection and monitoring approaches exist to capture landscape-livelihood information such as surveys, participatory GIS (PGIS), and remote sensing. However, these monitoring approaches are challenged by data collection and management burdens, timely integration of databases and data streams, aligning system requirements with local needs, and socio-technical issues associated with low-resource development contexts. Such monitoring approaches only provide static representation of livelihood-landscape interactions failing to capture the dynamic nature of vulnerabilities, and benefit only a small user base. We present a prototype of a mobile, open-source geospatial tool being collaboratively developed with the Ministries of Agriculture in Fiji and Tonga and local stakeholders, to address the above shortcomings of PGIS and other environmental monitoring and data sharing approaches. The tool is being developed using open-source mobile GIS technologies following a formal ICT for Development (ICT4D) framework. We discuss the results for each component of the ICT4D framework which involves multiple landscape stakeholders across the two Small Island Developing States. Based on the ICT4D user requirements analysis, we produced a prototype open-source mobile geospatial data collection, analysis and sharing tool. New dynamic spatial data layers related to landscape use and climate were specifically developed for use in the tool. We present the functionality of the tool alongside the results of field-testing with stakeholders in Fiji and Tonga