Remote Messenger (rmsg.exe) is a small application designed to allow sending popup notifications within a network using tcp/ip protocol.
It also comes with a small command line module that allows for passing through the client commands to the recieving machine thus making the life of an administrator easier. There are so many times that you had to go physically somewhere just to write ipconfig /flushdns or remote desktop to do something you could do just with a simple command.
This is not a hacking tool as it respects domain policies. It allows for an administrator to set it with higher priviledges than the user but it is in no way intended to be used as a trojan and although it could have easily been made to bypass windows security settings, great care has been taken not to go too far.