The number of mobile devices with Internet connectivity exponentially increases every year. Furthermore, these devices are more and more important not only in business contexts, but also in particular ones. The efficiency of a user performing a task with a mobile device can drastically vary because of its context dependency. Therefore, it is vital to measure the efficiency of the user regarding the surrounding environment. The current methods tend to discard the variation of characteristics of the context where a mobile application is executed. Through this work a new context and interaction model focused on mobile applications is exposed. First, the capture method that adds the minimum deviations caused by external factors to the assessment results has been studied. Then, a system based on a library for Android devices that captures and measures the defined model and the user efficiency is shown and validated.