In this paper, we describe design work with 36 children aged 9 and 10 in Bristol, United Kingdom. The design work was conducted using emerging mobile and wireless technology which has the potential to impact on the problematic issue of children's access to, use of, and safety within the wider urban environment. A series of workshops are described in which children were encouraged to think about their use of an outdoor space before their introduction to the technology. The children designed and created "soundscapes" in the outdoor environment. The future potential impact of the technology on children's spatial practice is discussed and the concept of children "tagging" environmental hazards is raised.