We could play a sound. Something like SWTOR's "Chat Awareness Ping". But we are limited to a subset of what is in the game as sounds (no custom sounds yet).
We could also put it as a notification on the screen (in addition to it comming in the chat).
We could even add another chat box just for whispers (see ChatSetup)
Personally I just have all my tabs enabeeld to show /tell messages. Even the group only/guild only ones. Keeping multiple tabs synched acrosss characters - that is what I made UCT for:
http://www.esoui.com/downloads/info4...dChatTabs.html