When a call comes in and you don't answer it, the app will be activated.
When a SMS or MMS message comes in and you don't read it, the app will be activated.
Once the app is activated, it will check if screen is off and start a timer if screen is off.
After the time of Alert Interval passes, the app will alert to you by sound and vibration.
If you don't stop the app, it will repeat its job until Alert Count exceeds.