biosensors and related info

Hello all,
    I am looking into the area of biosensors for my project and am
looking specifically at areas in which the validity of the sensor
itself be evaluated. The biosensors are crucial elements in any
application they are put into and they need to be relied on. But is
there anyone looking into the aspect of it going wayward and chances
of implementing something into the sensor itself which would "beep"
somebody if it's wavering from it's expected path.
Please let me know if there is any info in this regard anywhere.
This information would be very helpful to me.

Thanks a lot.

Bhanu Samarth