Boxcar (disclosure: I helped build it) will allow you to send remote pushes to your desktop and mobile devices. On the desktop, we partner with Growl to display messages as a pop-up.
FWIW, we also push Github notifications.
My program, lerner (http://github.com/zhemao/lerner) does something similar on Linux using libnotify.
Here is an example: http://stackoverflow.com/questions/1109786/growl-notificatio...