Alarm not based on neither sound nor vibration
Not part of the Apple eco-system but inexpensive at under 20 USD and fits your criteria…


  Shake-n-Wake
  
  Silent Vibrating Alarm Wrist Clock You will never oversleep again! Wear it on your wrist. Wake up without disturbing others. Silent vibrating alarm clock wont disturb others -Lightweight and Comfortable -Large LCD screen -One touch backlight allows for easy time telling -Vibrating or sound alarm selectable -Perfect for a reminder to take medication -Includes a wrist band or belt clip. -Runs on 1 AA battery - not included -Excellent clam shell package