Bukkit

The ability to add a sound, along with your title, has been added!

/region flag [region id] greeting-sound [sound name]
/region flag [region id] farewell-sound [sound name]

The sound name comes from Bukkit's sound enum (Which can be found here)

Example

If I wanted the sound of a chest opening to happen when I entered my region called "Kevin" I would use the following command;

/region flag kevin greeting-sound BLOCK_CHEST_OPEN