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.
wnr - Better than pomodoro, this timer app balances work and rest.
Talalarmo - Minimalistic android alarm
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows