A microcontroller for recording and storing physiological data includes an analog-to-digital converter for converting analog physiological sensor signals to digital signals, a sample buffer for holding a temporal sequence of the digital signals, a central processing unit (CPU), and a non-volatile memory. The non-volatile memory includes (i) a code storage encoding machine-readable data compression instructions that, when executed by the CPU, control the CPU to (a) transform the temporal sequence of the digital signals to produce transformed physiological data characterized by a set of transformation coefficients and (b) compress the set of transformation coefficients to generate compressed physiological data, and (ii) a data storage configured to contain several different instances of the compressed physiological data respectively associated with several different instances of the temporal sequence of the digital signals.