This holiday season, I created my own little mashup by combining this web service (created by Ben Hammersley) to track a FedEx package via RSS and the Yahoo Alerts service to notify my mobile phone when the FedEx status was updated.
The combination worked pretty well (Yahoo Alerts sent several false/duplicate updates). It would be nice if all of the major shipping carriers provided this as a service. Tracking multiple packages via RSS is much simpler via RSS than having to go ping individual websites. The option to couple this with SMS notification is a big plus for critical, can’t miss shipments.