Similar to what Everhour currently have for Google Chrome - https://chrome.google.com/webstore/detail/everhour-time-tracker/dnebklifojaaecmheejjopgjdljebpeo
Here is the Safari extension URL- https://everhour.com/addon/safari/Everhour%20Time%20Tracker.safariextz
Haven’t announced it yet ’cause waiting for Apple final approval. They have a looong review process.
But you can download it now.