I can see Goh creating a decive that can scan a wild pokemon and register it to the pokedex as if it were caught, but it would still be a wild pokemon. it would be helpful for getting legendaries or rare pokemon that don't want to be caught, like mewtwo.
Considering his parents had developed a portable device that detects the presence of Mew in wilderness it wouldn't be surprising if as a late teenager or during adulthood he would cooperate with other people with more knowledge inside technological field to develop other type of devices and projects regarding studying species. I believe that Clemont could be a good collaborator (as long the gadget wouldn't explode!).
The conventional Pokédexes do partial registrations whenever a species was seen by the users. The animé also provides detailed data whenever one is being analysed locally.
The closet concept to "register" and still remain a wild Pokémon is Pokémon Ranger with the Capture Styler technology. Its principle is connecting both the Ranger and the Wild Pokémon's hearts/feelings to be aligned and thus understanding each other without the need for deep communication or a Poké Ball capture. When I played the trilogy during curfew I liked to imagine how such a bonus it would be for a Pokémon Ranger to be simultaneously an Aura-User. Calming, recruiting and saving Pokémon would be a much easier task and it's something on Destiny's favour later in her life when she graduates as a Pokémon Ranger!
