I think that the notification feature should have an entire page for it self, with many options.
1 address
- gtalk notification on x confirmations
- email notification on x confirmations
...
2 address
- Skype notification on x confirmations
- Skype notification on y confirmations
All wallet addresses
- gtalk notification on h confirmations
...
User should be able to add/select more addresses.
You can set some limitations here, example:
- only 10 addresses
- only 50 notifications
You know how much you can offer for free
If the user wants more, he can pay something.
This can be another way to earn money, and if it will give good incomes ... I hope you will back to free transaction ( without your fee )