Hello codeforces community!
You can search and filter problems, import solved problems from Codeforces and add problems to a todo list. You can also check out upcoming contests from a contests calendar in the application which is powered by clist.by API and export upcoming contests you are interested in to your phone's calendar. Currently problem database consists of Codeforces and Codechef only, but we are planning to expand it later on.
P.S. Would you be interested in a feature which sends your phone a notification once when Codeforces system-test is over and another time when ratings are updated?