Set of daily quest that random ask for a pool of say 300 + math, Science, History quests (But Real world question, so the game can teach as well, no time limit on answer the questions though, so they can be researched). should give much of a award for all correct answer, but in the neighborhood of 25XP, 100gold.. I would write the questions in a database of your choosing if you like (I can separate the type, so you could have three types of dailies).
An hour warning after two hours of how long you have been playing, to tell you to take a break, get something to drink and stretch.
A tournament where you are going up against an actually randomly generate gauntlet, the higher you get the better the score, (Kind of like a huge mini-game).