Messaging from desktop
This sounds a lot to me like a sort of push notification system. The way I have implement this into my own foot print is to use growl/libnotify on the desktop and notify my android which allows me to have a central cloud based datastore for my alerts.

There is also the option of just emailing all your devices/contacts instead. One can find a Email To SMS Email Address List which lists the domains you would need to send a message to for your SMS/MMS communication to be transmitted.