Spontaneous interaction in ubiquitous computing settings requires a simple, well-understood means for users to communicate with devices in their nearby environment, some kind of equipment most people are familiar with, and a mechanism to determine whether certain entities can interact with each other. Mobile phones are a well-established means for people to communicate not only verbally, but also by using features such as the short message service (SMS). This paper shows how SMS can be used to interact with ubiquitous computing environments. It also presents a location service that associates particular entities with each other based on symbolic location. When spontaneous interaction is initiated by the environment and not by the human user, the concept of symbolic location is suitable to select entities to interact with.