Star Trek technology that we use today

Doctor McCoy could measure someone's vital signs by waving a sensor over someone's body and looking at a read-out on his tricorder.

Today, "tricorders" really exist. The "Scanadu" works by placing a tiny sensor on a patient's forehead. Through its sensor, and in a matter of seconds, the Scanadu measures heart rate, temperature, blood pressure, oxygen level and provides a complete ECG reading.