Power Nap App - Best napping timer with relaxing sleep sounds

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

Shhh Noise - A free sound generator designed to increase focus and relaxation.

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.

Rain Room - Listen to curated rain recordings to feel relaxed and cosy

Talalarmo - Minimalistic android alarm