Shell Commands

Is there a asterisk “application” that will run shell commands? Then I could do things like run voicemail thru Sphinx and have users recieve textual representations of email, or I can write an Embedded C program to open my garage door and run it by dialing an extension on my cell phone.

It is possible to run system shell commands using this application:

But, what I think you are actually looking for is the ability to pass control to an external program, have a look here: