Hopefully Korea gets rid of its 7-day quarantine rule soon. Until then, here are some apps I used when I was in the country a few years ago.
Naver Map (네이버지도)
Naver Map has a pretty good English version and its the Google Maps of Korea. It shows the best routes for driving/using public transport/walking.
Google Maps still works pretty well for restaurant recommendations in Seoul, Busan and on Jeju.
Subway Korea (지하철)
This is the most up to date map of subways in South Korea. You can put in your starting station and destination; they’ll do the rest.
There are a few apps with this function, but Subway Korea is the highest rated.
Seoul Bus (서울버스)
Was once very necessary, but Naver Map now has the same function.
Check it out though if you want a more specialized bus app.
Kakao T (카카오택시)
For when you're too tired to take public transport, Kakao T lets you call taxis.
This has info from the Seoul Metropolitan Government on the best attractions to visit in the city.
It’s full of interesting places that you wouldn’t find like restaurants, ticketing and an event calendar.
Daily Hotel (데일리호텔)
Daily Hotel offers great deals on rooms the following day when there are vacancies. I found great deals on nice hotels while traveling in around in Korea.