Many studies of ubiquitous computing systems involve deploying a system to a group of users who will be studied through direct observation, interviews and the gathering of system log data. However, such studies are often limited in the number of participants and duration of the trial, particularly if the researchers are providing the participants with hardware. Apple’s App Store and similar application repositories have become popular with smartphone users, yet few ubiquitous computing studies have yet utilised these distribution mechanisms. We describe our experiences of running a very large scale trial where such a distribution model is used to recruit thousands of users for a mobile system trial that can be run continuously with no constrained end date. We explain how we conducted such a trial, covering issues such as data logging and interviewing users based in several different continents. Benefits and potential shortcomings of running a trial in this way are discussed and we offer guidance on ways to help manage a large and disparate user-base using in-application feedback measures and web-based social networking applications. We describe how, through these methods, we were able to further the development of a piece of ubiquitous computing software through user-informed design on a mass scale.