SleepBot - SleepBot is a sleep tracking app available in Google Play and the Apple App Store.
TimeLeft - TimeLeft is a versatile desktop utility - it can be used as a countdown clock, reminder, clock...
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.
Talalarmo - Minimalistic android alarm
wnr - Better than pomodoro, this timer app balances work and rest.