This is really nice. I have been using the atom feed provided by https://crt.sh/ and an ifttt recipe to send me an email when a new cert is logged¹, but this service looks really nice and made exactly for this purpose.
When I first posted it on HN, it went offline literally seconds later in the Linode DDoS (it's now on AWS). Naturally, it's largely flown under the radar since.
¹https://www.linickx.com/monitor-for-fake-certificates-with-c...
edit: my ifttt recipe: https://ifttt.com/recipes/444453-get-notified-when-a-certifi...