The large variety of commercialized mobile devices, their reduced costs and their increased level of maturity makes them suitable for exploitation in an increasing number of contexts. However, the idiosyncrasies of interactive systems on mobile platforms raise many new challenges in terms of design, development and use. Such specific aspects include, dynamicity of contexts of use, interaction on the move and device management (e.g. power availability) that bring together many challenges and opportunities in every stages of the development process. This includes, for instances, designing various applications to be deployed on multiple devices to be used by a single user. Several research contributions started to tackle these challenges but few of them address the additional constraints raised by safety-critical systems. Safety critical systems designs call for well designed and implemented trade-offs between multiple properties such as safety, reliability' in addition to usability and UX. This position paper aims at presenting new challenges for designing, developing, evaluating and deploying future mobile UIs targeting at the domain of critical systems.