The suitable placement of a small number of calibrated piezo-resistive accelerometer devices may success to assess postures and motions reliably. This finding, which was obtained in a previous investigation, led to the further development of this methodology and to an extension from the laboratory to conditions of daily life. The intention was to validate the accelerometric assessment against behavior observation and to examine the retest reliability. Multiple number of students and patients are included for the obtaining the signal acquisition. © 2011 IEEE.