Here are the circuit diagrams for the biometric sensors for VitaMon. The amplifier circuitry for the EKG, galvanic skin response (skin conductance), and temperature sensors for the patient monitor were designed by Vadim Gerasimov. For most of the amplifier circuitry, Burr-Brown 4336 quad op-amp parts were used.
For the temperature sensor, the National Semiconductor LM35 precision temperature sensor is used since it does not require any explicit calibration, is accurate to +/- 1/4 degree (centigrade), and is low-power. The precision temperature amplifier is instantiated with just a standard op amp, using precision (1%) resistors in order to get precise values off the sensor.
The GSR sensor basically measure the skin conductance/resistance between two electrodes. The circuit basically instantiates a wheatstone bridge to find the unknown skin resistance value.
Here's a scan of the temperature and GSR circuits:
The EKG is the most tricky to get right, because of the very small potentials involved (on the order of mVs) as well as susceptibility to noise. For this the INA321 Burr-Brown instrumentation amplifier is used, in conjuction with a couple of other op-amps for filtering. The differential amplifier gets rid of the common mode noise, and an additional amplifer is used to hi-pass filter the signal to get rid of the dc bias. The resulting signal is then further amplified by another op-amp set up to as a low-pass filter to get the final signal for the hoarder.
Here's a scan of the ekg circuit: