Well lets be honest folks, if you are here, its because your prior app wasn't doing it for you any longer.
I too came from Package Buddy - loved the product and it met my needs until it was abandoned.
I'm here now (and have been for four years) because this is the best product I have found to accomplish my tracking needs.
Yes, auto-identification/auto-suggestion of the carrier is not the coding nightmare some of you seem to think it is, but it may not be on the top of oRRs priority list.
I'm know I am US biased, but even internationally, outside of the domestic mail services there are maybe a dozen big name carriers that carry the bulk of the parcels. Start there with parsing tracking id patterns and add additional carriers in batches.
If you knock out the common ones, most peoples normal package carriers will be detected.