If you know something suspicious is happening you can change your password (from the app) and throw the hacker out. You can also avoid rolling-hacks (ex: when your email is used to reset passwords on other services)
I'm not saying the service has no potential value, rather that it doesn't fulfill the "don't get hacked" reprise by notifying you after the fact.
The notification could allow you to fix the problem once it has happened but any hacker with reasonable sophistication can download data and change passwords in an automated fashion long before you can finish reading the notification.
The notification could allow you to fix the problem once it has happened but any hacker with reasonable sophistication can download data and change passwords in an automated fashion long before you can finish reading the notification.