Worldwide, the number of people at risk in landslide areas is increasing due to uncontrolled urbanisation and climate change impacts. The extent of relocation required usually overwhelms municipalities and administrations with limited financial resources. In the Colombian city of Medellín, self-built neighbourhoods stretch over mountains whose slopes give way and bury entire settlements. The German-Colombian research project Inform@Risk, together with residents of the informal settlements of Medellín, is developing a low-cost and low-maintenance early-warning system.