Sleep Cycle - Bio-alarm clock that wakes you up at optimal times based on your sleep patterns.

Gone - An ephemeral to-do list

Sleep as Android - Common alarm clocks ignore your sleep cycles, they wake you on schedule no matter your are currently in your deep sleep. Waking up from deep sleep is unpleasant, it makes you tired and it may negatively affect your productivity during the whole day.

Streaks - The to-do list that helps you form good habits.

Talalarmo - Minimalistic android alarm

Todoist - Todoist is a to-do list that helps you get organized, at work and in life.