It certainly can be realized, but the optical isolator would just be one component in such an application. This application is dealing with very low signal levels and has to be designed with low noise and high common noise rejection.
Because of the low signal strength there will most likely have to be some amplification performed before routing the signal with enough voltage/current required for going through an optical isolator. This implies a power source for the sensor circuit prior to the isolator, most likely low voltage battery(s). While most optical isolators are used in on/off switching mode, it's just a matter of proper DC bias and signal injection to pass an analog signal through such an isolator.
You could most likely get ALMOST as much isolation safety using small signal transformers between the signal probes and the existing amplifier circuit. However proper specifications and locating them will not be a simple task.
As many have implied, it's kind of important that you share your intent for such an application. If it's just for your personal use, experimental much as the link you posted from, that's one thing. If it's for use on others or for general sale then you really need to learn about all the legal requirements.
Lefty