Hey T2n
I have found three places where I was able to make calls.
1. The east side of Lone Pine Lake. A bit of a hike off of the main trail, but you can make a call from there.

2. The ridge right before Consultation Lake.

3. The Summit

I didn't try Trail Crest, but I would bet you could get reception there too.

I just did Whitney solo and my wife (and mother) both didn't like the idea. Look into the SPOT II GPS tracker/messenger. It not only allows your wife to track your progess, but you can send her pre-programmed messages. You can even send out an emergency message.

Here is the record of my Whitney Summit trip on Sept 7/8
http://spotwalla.com/tripViewer.php?id=1eb14c7e72bbf06a4

This thread talks about the SPOT II
http://www.whitneyzone.com/wz/ubbthreads.php/topics/7027/1