Calendar Alarm gives long and loud sounds
We made a loud and long alarm possible with an app called Calendar Alarm, now available in the app store. The alarm syncs with the default Calendar. There are 12 sounds to choose between and the sounds rings for 10 or 30 seconds. In the upcoming version (begin september 2010) we will also add a repeat/snooze.
App store name: Calendar Alarm
App store id: 367803799
Also don't forget to switch of the original Calendar ALert tone. You can do this as following: Go to the standard iPhone Settings, choose Sounds, scroll down to Calendar Alerts. The default is on , you just need to set the switch to off.