This talk will present a snapshot of some of the current projects underway in the CLARITY centre which contribute to the proposition of the sensor web. In particular we focus on lifelogging, tennis, cycling and environmental water quality monitoring as examples of sensor webs. The then present a summary of approaches taken to identifying the presence or absence of groups of semantic features, in video. The annual TRECVid activity has been benchmarking the effectiveness of various approaches since 2001 and we will examine what is the performance of these detectors, what are the trends in this area, and what is the state of the art. We will discover that the performance of individual detectors varies widely depending on the nature of the semantic feature, the quality of training data and its dependence on other detectors. There is a strong parallel between this and the way that sensors (environmental, physiological, etc.) which make up the sensor web, can also have poor accuracy levels when used in isolation but whose individual performances can be improved when used in combination.