The BCI community has a long-standing experience with one of the employed strategies for operating EEG-based BCI systems – the modulation of sensorimotor EEG reactivity induced by movement imagery tasks (Pfurtscheller et al., 1997; Neuper et al., 1999, 2006; Cincotti et al., 2003; Kübler et al., 2005). This makes possible the development of flexible and affordable BCI tools to objectify and to monitor individual MI execution both in terms of performance (relation between subject MI performance and subject level of accuracy in controlling BCI-operated basic applications) and compliance (identification of a correct MI task which is needed to achieve BCI-system control).