PIDU

PIDU stands for Personal Identification Display Unit, and it's primary function is to serve as identification. It was invented by the Commercium a long time ago, and while modern units have been improved drastically in performance, the old ones, that are now thousands of years old, worked as well. A lot of technology in the modern galaxy revolves around the PIDU and the accompanying brain implant. Neurological equipment like the PIDU has opened up a lot of opportunities for those with the physiology to use it. 
The PIDU unit consists of several things, most importantly a brain implant. A bare-bones PIDU unit connects to the eyes, ears, olfactory senses and the nerves, through the brain, allowing the owner of the PIDU to have a clearer picture of what is happening with their body at all times. 
The PIDU is non-invasive however, and many people never learn to properly utilize the PIDU - the PIDU essentially allows the user to conjure interfaces and graphics at will, which the PIDU implant generates, fooling the brain into thinking that said objects are present. The PIDU can trick the brain into believing that the owner is seeing things, hearing things or to a limited degree, even feeling things. 
PIDU units have natural restrictions, and can on purpose not mimic more than extremely basic feelings, such as touching a hard surface or touching a slightly softer surface, and it cannot mimic taste or smells. 
The PIDU has very limited hardware capabilities on it's own, being truthfully just a chip. Most pieces of modern equipment can be slaved to a PIDU unit, allowing them to broadcast to a PIDU unit (essentially live-stream to a PIDU). This way, a person with a music player could listen to music through their PIDU, no sound would actually play, but the subject would still think that they were hearing music. 
The PIDU cannot create any decisively unpleasant reactions, such as a deafening sound or an incredibly bright light. 
Few people have the technological understanding to operate a PIDU without essentially bringing up a non-existent keyboard or other similar user interface, that only they can see, to operate it, but this feature wasn't particularly popular before the scream. 
== PIDU Crime ==
PIDU units contain an identity profile, which is hard-coded into the PIDU. This exists to ensure that no one can do identity theft, thus eliminating quite a few otherwise potential aspects of cyber crime in such a modern age. 
Of course, it's still possible to tamper with the PIDU. The rumor has it, that the Exchange is such an important factor in galactic economy, that the Commercium is forced to tolerate them to an extent, and this is supposedly the reason why the Commercium hasn't done more to actively prevent PIDU tampering. 
It's possible to expand the capability of a PIDU unit, giving it the capability to switch between fake IDs - this method will work in some cases where there isn't a direct uplink to Commercium databanks, but the only way to ensure that a fake ID will actually hold up, is through corruption - namely with the Commercium. It's possible to pay to have a fake ID slipped into the databanks of the Commercium, and this will make an ID valid. Of course, even a validated ID will only stand up to so much investigation before it becomes apparent that it's a fake. 
Another frequently used option is scrambling. A scrambled PIDU uses certain aggressive hacking software to trick hardware around it into momentarily thinking it has successfully verified a PIDU unit. It only holds up for a short while before a signal will come back from the verification server. 
The only purpose of a scrambled PIDU is to shake surveillance. A person with a scrambled unit can't be tracked by use of their PIDU unless they are incredibly careless. 
Often, criminals combine the two options. 
== Surrogates ==
A surrogate is a person who has had their PIDU chip rigged so it can in fact be controlled from the outside. Surrogates often become surrogates if they are looking to get their PIDU scrambled and pick the wrong clinic, or they are forced in order to pay off a debt. Some have a limited surrogate device that can only be toggled at their consent, and warrants only limited control over their motions. 
Surrogates, or proxies as they are sometimes called, are extremely useful for criminals. Some prostitutes are surrogates and there are even illegal game shows featuring surrogates that are under the control of others. 
Many soldiers and agents have advanced hardware implanted, that is similar to how traditional surrogate hacks work, allowing a tech expert or someone else to work through them in a pinch, but the military versions only result in a strong suggestion, the surrogate himself has to allow the action to happen.