Information and communication technology are potentially significant tools in strengthening local initiatives towards sustainability. The Science and Technology (S&T) Framework for Sustainable Development provides a context for such development. This article describes a study aimed at examining how the existing mobile technologies of standard messaging service and wireless application protocol can be used to support the activities of an environmental grassroots organisation -London 21 Sustainability Network (henceforth London 21). Following the S&T Framework, it is clear that to realise the potential of these technologies a new mobile service should be effectively embedded into the structure and activity of the network. Using a participatory research approach, an extensive user requirements study with 273 participants was carried out to ensure that the development of the mobile service for London 21 fulfils the purposes, goals and expectations of the organisation.This article describes a Mobile Spatial Messaging Service, called EcoTEXT, which was developed and deployed for London 21. This service allows individuals to receive geographically targeted, action-orientated, time-relevant information via text messages on their mobile phones. The content of the service is information about upcoming local environmental events and activities, which match the interest of the user, when these events occur in close spatial proximity to where that user resides. This type of service represents a powerful new dimension for the provision of data-driven services in comparison to current textbased services. Location is giving the service additional meaning and value. The introduction of such a service into the organisation's communication toolkit offers the potential to create, supplement and strengthen social ties and interactions within the community.