Something that wouldn't be obvious to an observer but would be impossible not to notice for a user would be Augmented Reality mods. It's shown in sci-fi movies as something that looks like a HUD in the user's field of view, the stuff that overlays what they see with information.
It would be insanely useful in a space environment. There's the small stuff like just knowing what time it is without have to look at a watch, sure. But, think of a tourist finding himself on a station or colony. There could be signs everywhere in dozens of local languages, people all around talking in even more, lights, activity, advertisements, announcements, intimidating security types in black body armor, exotic smells - information overload! So confusing and overwhelming; how can he ever find his way? But, it's cool. It's ok. He has AR, so his connection to the station's wireless network lets it overlay a line that he can follow all the way to the door conveniently glowing green in his vision. Yay! He just found his hotel without getting lost in the crazy press of people.
Now, later, this same tourist is on a ship going somewhere else. Oh, no! Pirates are attacking. "Our cruisers can't repel firepower of that magnitude!" There are only seconds until the ship ends in a blue flash. Everybody is scrambling and racing to the escape pods. The artificial gravity is bouncing all over the place in wild fluctuations until it dies completely. The alarm to abandon ship is blaring, and the lights snap off, on, flutter, and the die. The only thing letting him see where he's going are the flashing warning lights and the flicker from a fire. Fire! Ohmygod, fire in space! It's pure chaos and hell with nothing but a horrible death unless he can make it to a pod. But, he has one lifeline: his AR overlay that still has information stored from just before the local network died with the rest of the systems. Follow that line for your life! Don't open the red door; red means there's open vacuum on the other side. Take the green one and go until you see the blue arrow pointing to the lifeboat's hatch.
Later, he's made it back home. It's such a boring job repairing life support systems in this mining colony on some moon. He's walking down a long tunnel full of wires and pipes until he finds what he's looking for: a junction panel conveniently marked with an electronic sign that says, "Hey! Something's wrong here." Just by looking at it, he can see that the power line going into the panel is running at 98% efficiency, but the line going out is only at 0.9%. It's time to get to work and fix it. How helpful it is that a pop-up of the schematics and every bit of information he needs appears off to one side of his vision.
If he's lucky, he can get done in time to meet the woman he met on a social networking site for dinner. He even copy and pasted her details, so that when he looks at her, he can instantly see that fried Caldari seafood is something she likes. The cook is already starting to make some, and he's able to see the nutritional information, expiration date, and preparation instructions thanks to the information encoded on the package's RFID. Meanwhile, she works on a safety crew and is tracking down the dot from the RFID chip of a child that got lost after going to explore the mines. And, in the park area on the main level, a group of teenagers are running around, pointing at each other, and shouting, "Pew pew!", while they play Halo 9847865 AR Edition in a multiplayer deathmatch.
That's all with just vision. Imagine someone wired for sound (literally), or touch, smell, and taste.
Of course, there's always the opportunity for spam and malware. Who wants to walk along a station level full of casinos all blaring pop-ups of how "YOU COULD BE A WINNER!" or walk down the grocery store aisle with things shouting at you that they offer "33% more for the same price as the leading competitor!"? Or, more dangerously, you could be 'jammed' by someone overloading you with illusionary lights and sound like an electronic flashbang. Worst would be a hack with a realistic overlay of reality - what looks like the bathroom door to you is actually an airlock!