Mountain Lion gained a Reminders app that looks at works much like its iOS counterpart. One advantage the Mac version has over its little brother is support for adding tasks with natural language.
If you create a new task like “remind me to eat lunch at 12pm tomorrow,” Reminders for Mac will figure out what you mean and create a task called “eat lunch,” then set a reminder to sound at 12pm the next day.

via Lex Friedman