Lightweight downloadable applications, or apps, do everything from identify songs playing on the radio to submitting the weekly order for your grocery shopping. They are a key aspect of the dramatic shift that the iPhone and similar devices have brought to the mobile phone market. Always on, always close at hand, and typically aware of where they - and you - are in the world, the current generation of smartphone offers a widely distributed opportunity that developers have been quick to exploit. The author considers how data from the public sector is used in a number of these apps and concludes that, as we move past the enthusiasm of early adopters and brand managers, there are opportunities to ensure that PSI lies at the heart of a plethora of apps, delivering real and sustainable value to citizens across Europe. It may, however, require a wide and possibly free dissemination of data in order to encourage the use of PSI in as many contexts as possible.