Cybernetic Replacements

Any cybernetic device which replaces an outwardly observable part of the body AND which requires a neurological connection to function is a cybernetic replacement.   Cybernetic replacements for nearly any body part exist, though the most commonly replaced are arms (hands, fingers), legs (feet, toes), eyes, ears, and throat/voicebox. With that said, it is not entirely uncommon to see someone with a part of their face or torso replaced, or anything else.   Cybernetic replacements are nearly always customized to the user's needs, and there is a wide market for customization options of all kinds.  

Legality

In most places, it is illegal for civilian doctors to perform a cybernetic replacement surgery unless medically necessary. This rarely stops anyone, as "medically necessary" often just requires a doctor's say-so and it's rare that a court will punish a doctor if they can prove the patient consented to the surgery.   It is both illegal and considered ethically vile to perform any cybernetic surgery, but especially a replacement surgery, against a patient's will. Not only will almost all governments prosecute and punish doctors who do so, but a large majority of criminals and criminal organizations refuse to tolerate such actions as well. In most circles, it is seen as a violation of bodily autonomy akin to rape.  

Installation

Cybernetic replacements are widely available now, and have been for several decades by the 2030's. Besides being the industry standard for replacing medically lost or damaged body parts, there is a growing subsection of people voluntarily replacing their living and perfectly healthy body parts with cybernetics.   Living body parts which are removed may be stored in cryotanks for later re-attachment. For a fee, these can be reserved for the original owner, or they can be sold or donated to body banks for body grafting or scientific use.   The quality of replacements varies, but there is a minimum standard to which the vast majority of manufacturers adheres. Low-quality bootleg cybernetics operations generally struggle to get off the ground, due to horror stories and urban legends that went around in the early days, scaring most people away from disreputable sources.  

Control

Cybernetic replacements are built to be integrated directly with the recipient's nervous system. By default, there is no conscious mental link to the replacement; the owner does not "think" the commands at the cybernetic, but simply uses it the way they would use their natural body part. Extra functionalities, therefore, feel like physical extensions of the body. Weapons or tools in cyberlimbs are operated using "muscles" that the user must learn to control, different modes are activated by learning to focus eyes or ears differently, etc.   The exception, here, functions which require a direct, conscious mind link to operate. For these functions, a neural processor must be installed, and the functionality must be wired into it just as if it was installed as a standalone cybernetic enhancement.   An example of this dichotomy is Athena's cybernetic eyes. Her Text Marquee functionality requires no input from her whatsoever - it is connected to her Agent via short-range radio waves, and will function so long as her Agent is within a certain distance of her person. Her Telescopic Vision is a "natural" enhancement, and she had to learn to control it by concentrating on distant objects until they became clearer. However, her Video Playback and Livefeed functionalities are mentally controlled through her neural processor - she thinks specific commands very loudly in order to operate those functions.  

Sensory Feedback

Cybernetic replacements are, by default, equipped with a suite of appropriate sensors and fully integrated into the nervous system of the wearer.  As a result, they provide sensory feedback that is as close to natural as possible for that cybernetic's construction, and can include pressure, temperature, directional, and pain sensitivity.  Cyberlimbs with skinlike coverings generally provide the most nuanced feedback, with RealSkinn being the most realistic experience.     Damage to the internal workings of a cyberlimb generally transmit to the user as feelings of discomfort, stiffness, or lack of mobility rather than as pain.  And for those cyberlimbs that do provide a realistic pain response, there is often a maximum pain cap, beyond which point a safety override is tripped and the pain is abruptly cut off.   All cybernetic replacements that meet minimum industry standards come equipped with a manual sensory override, which is used to turn off all sensory feedback before a cybernetic is serviced.  This override is not easily accessible and generally requires specialized tools and knowledge to operate.