A monitoring app for new comments on your favorite HN posts

Thinking of the following weekend project, which would allow users to get notified over email whenever a HN post in their favorites, gets new comments or updates. Could be your post or someone else.

It could work as follows:

- Go to HN and find a post you like, visit the post page like https://news.ycombinator.com/item?id=1 - Add it to your favorites list by clicking [favorite] right at the top

The following signup needs to be done only once:

- visit https://todo-hn-notifier.com - sign in with email - provide your HN username

Whenever a new comment appears in one of the favorite posts, an email is being sent. (With an easy unsubscribe link)

WDYT? Would you find such a web service useful? Any extra features would be cool to add?

Thank you.