How can I "say" to another Mac?
Since the two Mac are in the same house, I assume they're both on the same network.

First of all, you need to activate Remote Login on the Mac where you want the sound out.

Go to System Preferences &gt; Sharing and check the Remote Login checkbox.
Then, using your computer, open Terminal and type this

ssh &lt;user&gt;@&lt;computer name.local&gt;


Where &lt;user&gt; is your wife login and &lt;computer name&gt; is the name of the other computer.

Now, it's as if you're having Terminal open on your wife's computer and you can say whatever you like.