Parcels Tracks Packages, Even From The Post Office

I recently installed Parcels on my phone, which is an Android app that obtains package tracking information from a variety of different shipping companies, as well as the U.S. Postal Service (USPS). My previous experience with package tracking from the USPS has been disappointing because their web site only provided information after the package was delivered, making it effectively a package delivery confirmation service rather than a package tracking service.