Landslide is a frequent hazard, which causes thousands of fatalities annually worldwide. However, the incidents are predictable if there is appropriate monitoring equipment. In general, slopes, especially rock slopes, usually have a few minor movements before they completely slide down. The signals occur from a few seconds to a few weeks before any noticeable failures. Currently, there are plenty of slope monitoring devices, but they are expensive, complex, and specialised for large-scale mass wasting. There is a need for affordable devices for both domestic and public use. This paper summarises the challenges involved in the design of a low-cost self-assembly slope-stability monitoring device. The device uses the Light Detection and Ranging technology, which sends a light beam to a slope and captures the reflection. Based on the travel time, the distance from the device to a point on the slope is calculated. The continuous measurement detects any imminent slope movement. The device is accurate, durable, and can operate under different working conditions with a high degree of reliability.