Applications that rely on mobile devices for user interaction must be mindful of the user's limited attention, which will typically be split between several competing tasks. Content delivery in such systems must be adapted closely to users' evolving situations and shifting priorities, in a way that cannot be accomplished using static filtering determined a priori. We propose a more dynamic context-driven approach to content delivery. We demonstrate our approach using Scatterbox, a pervasive computing application we have developed which performs sensor fusion to derive a user's current situation. Based on the user's level of interruptibility, Scatterbox prioritises and forwards relevant messages to their mobile phone. We draw conclusions from a preliminary evaluation of the system. R