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Hypospray and non-invasive surgery
McCoy's "Hypospray," which allowed for instantaneous, bloodless, and needle-free liquid injections, hasn't quite made it in terms of handheld portability yet to every medical office, but a real-life equivalent for use in mass-dosage scenarios exists as the jet injector, and is used for vaccinations by the Department of Defense and other government and relief agencies around the world.
While the truly non-invasive surgery employed on the original Star Trek and TNG shows for generalized use still remains largely science fiction, some procedures such as Stereotactic Radiosurgery for treating specific types of tumors, allow for non-invasive surgery on brain tissue using focused radiation beams.
And while the hand-held directed energy "Phaser" guns used for combat against hostile aliens still remain a fantasy, LASIK surgery using focused low-wattage lasers to correct vision is now well on its way to making eye glasses and contact lenses obsolete.
The "Vorta Command" headset
First shown in Star Trek: Deep Space Nine, the command headset employed by the Dominion "Vorta" overseers of the brutal Jem'Hadar forces was used to have complete situational awareness while piloting their attack ships.
Today, we know this product as Google Glass.
One of the most awe-inspiring technologies that has been in every single one of the Star Trek series has been the "Replicator," a device that is able to produce any object, of any complexity, either inorganic or organic in nature, whether it be food or machines, purely by combining raw matter and energy from patterns stored in the computer and re-arranging particles at a sub-atomic level.
In Star Trek, the "Replicator" was an offshoot of the "Transporter" technology that allowed for de-materialization and re-materialization of objects and beings at vast distances.
While this sort of power over pure matter and energy is probably hundreds, if not thousands, of years beyond our current reach, the "Replicator" is here in a much more primitive form as the 3D printer, which can produce fairly complex objects for rapid prototype and manufacture using any number of materials, including plastics, metals, and also proteins and other organic substances.