Reimagining of the alarm.

The block is still a "place-it-and-use-it" kind of deal, however now
only you can hear it. You can now right-click it and switch it to
multiplayer mode, in which case not only you, but the players you set
will hear it. Switching it back to singleplayer mode will make it so
that only you can hear it again. It is not complete, so any help is
welcome.