Notification about Tasks not in progress during the time period

Hi,

we have a Project with several tasks. Now, i recognized, that i don't get email notification about the delay of the tasks. 
Would it be possible to do somehting about that?

I need to know, if there are People assigned for a task and they are not active within the assigned period of time. After 50% of the time, it would be also nice to get a notification about the delay! And if the timeperiod expires, it would be also nice to get informed. 

At the moment, i am doing this with the Dashboard but this is not enough i think. Perhaps a possibility to enter a special Emailadress for this problem like the teamleader. Would be great to keep folks on track.

Greetings