Would anyone care to tweet their high score on an arcade game? Is there a way to monitize the high score? "Insert quarter to tweet score."
Logging in not withstanding, I don't have a good idea for that. The best I've come up with is a qr code on your phone you put in front of a camera.
Japan has been building machines with networked high-scores/progress saving since the late 90s/early 00s... it's just barely made it's way to the USA.
Konami games, mostly Bemani games (like DDR/Beatmania) have "E-Amusement" pass. these used to give you magnetic cards but then later switched to rfid cards that keep track of your score and even allows you to "unlock" new songs within the game, all the scores are tracked online for national rankings...
Sega has been doing Magnetic cards for progress saving and online ranking for nearly as long with most of their titles, I even have an Initial D card in my wallet right now with my own drift-car build saved on it

Japan has a lot of other games like tactical RPGs and sports management sims that rely heavily on being able to save your progress and come back another day... Heck even fighting games in Japan now ship with 1 player panels and simply connect you to another player over the network for versus play.
A lot of these games give the OP and option to have a non-gaming "terminal" setup where players can manage their account or view their stats without having to occupy one of the actual gaming machines.
In a lot of cases if you want a card there is an extra cost when issuing the card, but players who want to be able to save their progress or keep track of their scores gladly hand it over.
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In the US a lot of competitive arcades like FunSpot and Galloping Ghost use Aurcade.com to keep track of all of their scores, but it's old school, and requires the scores be verified by a ref, you can upload your own scores manually but they're considered unofficial.
I'm going somewhere with all of this.....
IMO if you wanted to make this work with games that weren't designed with such a system in mind I'd borrow ideas from what the Japanese game companies have already done. Then I'd recommend having people register an account up front at a terminal somewhere... create an account with a user/pass/initials/and link it to their social media... charge them a registration fee of maybe $5 or $10 and issue them a card.
Then on the game they swipe their card before playing and you have a module setup to capture the high score and communicate it back to the central server where they've already registered and it can determine if it's going to tweet or whatever.
If someone wants to tweet their high score they're probably just going to take a picture of the screen and tweet that... most people who care are people who are competitive and want to work towards earning a record... in this case you really want a system that tracks a person's score over a period of time and is able to report scores in a somewhat official capacity.