Run external command on client

Is there any way I can run executables on the local client (Windows/Linux)? Either triggered from the server or the client? 

There are several things I would like to do:

- open a browser from the panelsoftware (open WebTV for example)

- change window focus (bring certain application windows to front)

- wake/sleep the screen based on actions (movement or alarm status)

- halt/reboot the machine

- change the volume/mute

Thanks!