This is currently already possible with the imap email content sensor with a little templating.
That said, something built in would be simpler, provided it is easy to set up. I think the new USPS sensor works by scraping the web interface, so it wouldn’t likely be easy to adapt to the UPS site.
UPS does offer its own API.
Shippo offers a single API for multiple shippers. It might be another option for this. Haven’t dug into the docs too deeply yet.
I found a few other projects on github, but most haven’t been updated in awhile.