WakeMe is a free to use wakeup and reminder service created by Code & Pixel. We at Code & Pixel don't have much time to sleep. That means it's rough to get up, and simply answering a call isn't enough.
WakeMe makes sure that you're up by asking you to answer either a math problem you'd be able to answer if you were awake, or one of your customized questions. Get the answer wrong and it will keep calling.