There are many ways to play koi-koi in video games, including in Sakura Wars and Yakuza games, where I first experienced them. I ended up getting my own hanafuda deck (from Nintendo, they still make them) and learning how to play koi-koi and some of its many, many variations of rules and scoring systems. It's a fun game, and the rules really aren't that complicated -- it's just a steep learning curve for getting to know what all of the cards are. (A cheat sheet or two can go a long way when you're starting out.)

Pocket Hanafuda for the Game Boy Color lets you play koi-koi as well as hana-awase on the go, against the computer AI. The cards appear on screen well enough, and so long as you know the basic rules you'll get the hang of it soon enough. I think the AI is cheap and totally cheats at times, but this is a Game Boy Color game lol. Not a bad way to kill some time, and there's something about the GBC pixel art that I really dig for the cards themselves.