Hello, I am thinking of doing experiments with Arduino on medical sensors as a hobby, nothing for selling... Any idea what low cost sensor (under $200) I can use?
You should look at how pulse oximeters work. They seem to just use an LED and perhaps a pressure sensor to give your pulse rate plus blood oxygen saturation. Very useful devices at the present time.
Read the specifications, the data sheet,of hte sensor. Most likely any Arduino would work.