Systems Management

I would also be interested in hearing if anyone has a tool or exe for this?

You could deploy a custom application that does it but that's hopefully not the easiest way.

I think it all depends on why you're sending the message. You could simply write a VBScript and then set that up as a package and deploy it. If you need to send messages on a regular basis you should look into login scripts. You can set a GPO and then set a login script to be executed on the machine upon login. Or you could display a message at the CTRL+ALT+DEL screen simply by adjusting the GPO settings.

So there's all sorts of methods...