2.11 - Okay, *now* whispers cross-server. Really. Trust me.
2.1 - now whispers cross-server
2.02 - won't try to whisper people cross-servers, since that's not possible yet
2.01 - bugfix for flight master bug, loss of control bug
2.0 - updated ToC for WoW 3.3, and added /chyw command for manual range-check-and-whisper in macros
1.6 - added throttling of whispers; default is one per 10 seconds per player
1.5 - added slash commands to turn on and off notifications, and to set the messages sent
1.0 - first version
If you're already out of range when you start the spell cast, Can't Heal You won't send a whisper. This can be worked around by making a macro using the /chyw command (described in the README)
It only whispers the target of a spell. For example, if you do Greater Blessing of Wisdom, and the target is in range, but other party/raid members aren't, those who aren't won't get whispered, since they're not being directly targeted.