The document discusses how location data and context awareness can be used to create ambient and invisible interfaces. It provides examples of early wearable and context-aware devices from the 1980s and discusses how modern smartphones have GPS and other sensors that enable new location-based applications. These applications can use a user's location to automatically check them into places, trigger reminders and events, and control home automation. The document envisions a future where location data and awareness of context allows software to act as a "robot working for you behind the scenes" in invisible ways.