Apparatus for determining and/or visualising and/or monitoring vital signs such as the respiratory rate and/or heart rate of a user, the apparatus comprising an accelerometer and a processor wherein the accelerometer is contained within a housing and configured to generate, in use, when the housing is placed in contact with the users upper body, a signal in response to motion of the users body and the processor is configured to receive the signal from the accelerometer and to process the signal to determine, and optionally cause display of, the vital sign. The apparatus may be implemented by a suitably-programmed mobile device (e.g. a smart phone having a built-in accelerometer). Embodiments enable user input, which is intended to be provided at specific times across a plurality of breaths or heartbeats, to cause the processor to provide an indication as to whether the user is concentrating on his or her breathing or heartbeat. This may be used to engender a state of mindfulness on the part of the user, for example to provide therapy to counter the effects of stress, anxiety, pain, depression or addiction disorders, or other psychiatric conditions. The apparatus may also be used for diagnostic purposes, for example identifying respiratory rate associated with a respiratory problem, or identifying heart rate characteristic associated with a heart-related problem.Appareil permettant de déterminer et/ou de visualiser et/ou de contrôler les signes vitaux tels que le rythme respiratoire et/ou le rythme cardiaque dun utilisateur, lappareil comprenant un accéléromètre et un processeur laccéléromètre est contenu dans un boîtier et conçu pour produire, lors de lutilisation, quand le boîtier est placé en contact avec le corps supérieur de lutilisateur, un signal en réponse au mouvement du corps de lutilisateur et le processeur est conçu pour recevoir le signal provenant de laccéléromètre et pour traiter le signal afin de déterminer le signe vital, et éventuellement de provo
