'This master thesis documents the research, design, and evaluation of a context-aware system which actively acquires user attention. Based on the results of an ethnomethodological study of supermarket shopping we design and implement a Context-Aware Shopping Trolley (CaST) that aims at lowering the complexity of supermarket shopping for its users. An extensive evaluation was carried out during the span of one week, where 18 participants took part in a field experiment in a Føtex supermarket. These participants were split into two groups. This yields the following results of how the implemented prototype of CaST supports shopping:  Users of CaST travelled a significantly short distance compared to users with shopping lists  CaST users generally collected the products in the same order which the shopping list users did not  In their subjective workload assessment CaST users reported a significantly lower mental workload compared to the shopping list users. Based on these results we conclude that CaST lowered the complexity of the shopping task.'