Show HN: Track your stamped first class letter

Recently, tired of going to post office to certify some letters (i.e. Tax returns, Bills etc.), I developed this tool. Mostly for personal use. Just post here in case someone interested.

Usage: Print the barcode on the envelope, track it later with serial number.

This is awesome! Thanks so much.

I think a natural extension of this could be

a) an API or CLI tool b) a minder service that logs / reminds when letter is delivered.