Summarising from a group of sensors
Depending on how you want to process the data and the driving current you have available, you can use a simple non-linearity to provide you with a maximum voltage. All you need is an element that behaves non-linearly with respect to the voltage across it.

Assuming your sensor outputs are low impedance, the simplest version of this would be:







simulate this circuit &ndash; Schematic created using CircuitLab

Vmax will be approximately equal to the largest voltage in all the sensors minus a diode drop. Likewise Vmin will be approximately equal to the lowest voltage in all the sensors plus a diode drop.

As the voltage-current dependence of a diode is exponential Vmax and Vmin will be close to the average voltage when all the sensors are about the same, but will exponentially deviate from this. As there is roughly a factor of 3 in current every 30mV of deviation, if the outputs are more than ~100mV apart, the contribution of the lower/higher voltage outputs would be negligible.

You can think of the circuit as a multi-input voltage divider (average circuit) but the non-linear diodes take the place of the resistors. If all the voltages are close to being the same (and the diodes are perfectly matched) the output is simply the average of the inputs (minus a diode drop, of course). But, the further the average deviates from any specific input the diode will exponentially reduce (or increase) its current leading whichever diode has the largest voltage across it to provide the most current to the resistor. At about 100mV differential the effect of all other diodes on the output voltage will be less than 1/10th of the effect of the dominant input.

Note that this diode structure is what you get with most interface clamping diodes. So this could be implemented with one IC and a couple resistors.