US Patent 7912852 Search-caching and threshold alerting for commerce sites

Users can be notified when information becomes available, such as when an item is available for purchase at some point in the future. Users can indicate to receive information about the item using a desired notification type, such as an email message or text message. A notification then can be sent to the user using the indicated type of notification when the item, or information about the item, subsequently becomes available through the system.