We have a plugin to press keys on keyboard ,but I’m not sure if it can trigger systemwide hotkeys.
see http://www.monkeybreadsoftware.net/module-remotecontrolmbs.shtml
Why not get a screenshot directly yourself?
see http://www.monkeybreadsoftware.net/pluginpart-screenshot.shtml
or just a screenshot rendering of a window?
see http://www.monkeybreadsoftware.net/module-cgwindowmbs.shtml