To ensure I don't forget to rotate/extend one of the subkeys of my PGP key, I created a little monitoring tool.
I wanted something that reminds me well before my published PGP key shows sign of expiry.
And I wanted it built in a way so it can be used in a simple cronjob to continuously nag me until the expiring key has been replaced. 😈

So pgp-expiry-monitor was born.
It takes two parameters, the URL of a PGP key and the number of days in advance it should start warning.
If all is fine and the PGP key does not contain any expiring keys, it returns without any output. Thus ideal for a cronjob.