Though setting a phone to constantly vibrate may seem a bit unusual, there are a few practical reasons for doing it. For example, you may need to drain your cell phone's battery before replacing it, or you may want to test the life of the battery. By setting your phone to vibrate and turning your alarm on, you can set your phone to constantly vibrate, provided you do not answer the alarm.
Set your cell phone's ringtone to "Vibrate."
Select "Menu." Select "Tools."
Select "Alarm" or "Alarm Clock," depending on your cell phone.
Set the alarm to a time close to the current time. When the alarm goes off, do not answer it. As long as the alarm is not answered, your cell phone will constantly vibrate.