I been looking for the same thing. The closest i got was the AlarAutomation mod from this URL:

http://wow.aspide.it

This one has an option that should let u forward /w to some other char in your friendlist....

However, i did not get it to work in my setup. But maby it's easy to fix. If you do try this addon, and get the /w forward to work please post a msg here so that we know...

// Ztar