I understand what you say but for an application that is there to remember you of something, I think it should alarm under all circumstances.
Alarming through sound is a quite vital feature for alarms/timers. For games, the gameplay (ex few exceptions)isn't hurt by no sound. Ofcourse the game experience may be hurt, though.

I don't know much but would using libalarm an solution? It's just a shout coming from the library name, without any real knowledge about what libalarm really does...