I would like to get notified via mail whenever there is a new item on the review site, like it's possible with tags. Is this possible and if yes: How?
No, let's not do that. (I have down voted your feature request for that reason, not because you asked a bad question).
First of all reviews are highly volatile (or at least they should be) on most sites. By the time you receive an email the review item or queue (still not sure what you want to follow) is probably gone/handled.
I'm active on Stack Overflow and have the Close Vote privilege which opens the close vote queue for me. I don't fancy getting notifications for available reviews in that queue (currently sitting at around 10K).
There is one other nasty thing with the current /review implementation and that is its performance. That isn't great to say the least and causes trouble, specially on Stack Overflow, now and then. To add more strain to this functionality without a proper re-engineering would only cause more problems, not less.
You can however check if a userscript might help in addressing your immediate needs. There are a couple available at the moment:
- Review Stalker Reloaded: A cross-site dashboard for reviews
- Review Stalker user script
- Review Queue Desktop Notification Script
Give them a testrun to see if they fit in your workflow.