NetSupport Page supports an alert mechanism which takes a ‘roll-your-own’ approach. Provided is an AppleScript application ‘shell’ which you can modify to interface with your favorite apps (PageNow, Claris eMailer, etc.).
Open and modify the NSP Alert application with Apple’s Script Editor or more powerful third-party AppleScript editor.
Simply place the NSP Alert application in the folder with the NSP application to activate your script. NSP will launch (and leave open) the AppleScript application and send it an event when any zone or device changes status (up or down). For more details, see the comments and sample code in the NSP Alert shell application.