Launched in 2012, ELIPSS (Longitudinal Internet Studies for Social Sciences) is the first French online representative panel dedicated to the social sciences research community. Each panel member is provided with a touch screen tablet and a 4G connection. The project has now hit its stride with around 2500 panel members and 70 surveys conducted so far. The Center for Socio-Political Data (CDSP) is responsible for the implementation of this project within the DIME-SHS (Data, infrastructures and survey methods in the humanities and social sciences) consortium. The CDSP IT team designs the software tools that collect data and paradata from the ELIPSS panel. These tools range from web services facilitating fieldwork management to a tailor-made Android application for collecting data directly from devices. First, designing an Android application collecting data for research purposes represents a real challenge. Very few guidelines are publicly available except for designing market-oriented mobile applications. Second, for the ELIPSS project, conflicting objectives have to be reconciled. One survey is fielded monthly and tight deadline are regularly to be met. This presentation will provide a concrete view of the design process of a mobile application for data and paradata collection from an online panel. We’ll also provide a feedback on how to collaborate with a device manufacturer, how to deal with confidentiality concerns in data and paradata collection, how to address ergonomy issues when designing questionnaires, and generally how to address complex research questions.