Sensor-Derived Measures of Motor and Cognitive Functions in People With Multiple Sclerosis Using Unsupervised Smartphone-Based Assessments: Proof-of-Concept Study - Matthew Scaramozza; Aurélie Ruet; Patrizia A Chiesa; Laïtissia Ahamada; Emmanuel Bartholomé; Loïc Carment; Julie Charre-Morin; Gautier Cosne; Léa Diouf; Christine C Guo; Adrien Juraver; Christoph M Kanzler; et al. (JMIR Formative Research)