Quite a few... Off the top of my head:

- Track emails sent using Apple Mail https://bigballi.com/track-emails

- Add PurpleAir reading to your Apple Watch https://bigballi.com/purpleair

- WhatsApp send message without adding to contacts https://bigballi.com/wa

- Create your own easy to remember zoom landing page https://myzoom.me/

- Extract all email addresses from Gmail mailbox

- Crop & post-process GoPro videos

- Amazon price drop notifier