Habitica is a combination task manager/RPG whose main aim is to help you create habits and remember tasks in a fun and pleasant way. Basically you create your own avatar and gain experience and coins as you complete your daily tasks.
You can choose which activities give you experience and gold. Checking your email in the morning could be one of them, or riding a bike for half an hour a day. Or you can enter specific activities and appointments to give you experience as well. The experience you get varies with the difficulty level you set for yourself.
As you get experience, you can level up and customize your avatar. And with the money you get you can buy all sorts of classic RPG items: swords, armors, shields, axes, etc. All these items change the appearance of your character.
Habitica is a pretty interesting app, especially for those who need a small incentive to complete their to-do list. In the end, it's an application where you can add your tasks and appointments ... with the added fun of playing an RPG.