Have you lost your phone? Send an SMS to your phone and your alarm volume will be set to 100% and your ringtone will start playing for 30 sec. It can be started by sending the keywords "Lost Phone", "Lost phone", "lost Phone", "lost phone" or "LOST PHONE" in the SMS (Without the quotes).
[DOES NOT require a ROOTED device]
Update 1: Added two more cases to the keywords to trigger the flow. I don't plan to add more upper or lower case keywords.
Rate and review within the app in the Community section.