On the K700i, the AT*ECAP=(1-8),(0-2) command apparently depresses the
camera button.  My short test gave ERROR.

AT*EAPP can send commands to the various applications, including the
Messaging App, but my first impression is that it only works for SMS.

Other than that, I searched through the AT command Design Guide for the
K7/Z1010, and the word "message" only showed up for SMS and various
AT-related messages.

I would recommend you go to SE's Developer Zone, register as a
developer, and download the latest AT-command guide.