While I try to get Web 2.0 Expo darling du jour Fireball working (still no luck), I thought it'd be worth covering another location service for Twitter: Trackthis. You tell it a package tracking number from FedEx, UPS, USPS, or DHL, and it will Twitter you back whenever there's an update from the shipper.
Yes, there are other ways to get this data, but there are advantages to using Trackthis: First, you can attach a descriptor to your query (like "lamp shade"). Second, you can use Twitter to easily change your message delivery options: you can quickly turn on or off SMS updates for Trackthis alerts, for example. This may be useful.