The concept of motional emf is very useful as it has many different applications in the real world. Physicians use motional emf to essentially determine the velocity (and therefore the flow rate) of blood as it flows through blood vessels (such as the artery). The apparatus that measures the velocity using motional emf is known as the electromagnetic blood flow meter. You essentially take the blood vessel and connect two electrodes to the opposite ends of the vessel so that the distance between the electrodes is equal to the diameter of the blood vessel. You connect these electrodes to a voltmeter that is capable of detecting an induced motional emf. You then create a uniform magnetic field around the blood vessel in the region where the electrodes were placed. Blood generally contains many different charged molecules and particles and when it flows past the electrodes within a constant magnetic field, it acts as if it was a conductor and therefore induced a motional emf between the two electrodes. This in turn induces an electric current. Using this setup, you can measure the velocity of the blood within the vessel.