Sleep Cycle - Bio-alarm clock that wakes you up at optimal times based on your sleep patterns.
Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
SleepBot - SleepBot is a sleep tracking app available in Google Play and the Apple App Store.
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows
Talalarmo - Minimalistic android alarm
SnapTimer - SnapTimer is a simple, free, portable countdown timer for Windows.