OnDemand Alerts
Want to get pinged when a movie becomes available OnDemand? Simply click its AlertMe button. ViewGuide handles the rest.
You can get Alerts for every movie or show in a Viewlist or for individual titles. For instance, click AlertMe for a list of movies you'd like to see, and then you'll be alerted when any movie currently in the list comes OnDemand, even as you add and remove movies from it.
Netflix Update: During November 2014, Netflix shutdown the ability for services like Viewguide to query movie availability. Viewguide's OnDemand Alerts still supports iTunes, Amazon and YouTube.
Alert Preferences
Click Edit OD Alerts on the top left of your Member Profile page to see your Alert preferences.
Here you can turn alerts on and off, and set which services to be alerted about, e.g., Amazon, iTunes, YouTube.
Your OnDemand Alerts page also allows you to remove alerts for movies and shows, and add more.
Alert On 
OD Alerts are a free service, as is all of ViewGuide. Simply join ViewGuide directly or via the Facebook login to get started.
Questions? Click here.