1. using the location from your mobile device, add your travel time to the selected notification time. Example:
you are currently 15 minutes from the location of the meeting and the notification was set at 5 minutes, the notification would actually go off 20 minutes before the start of the meeting.

2. you would see if other guests of the meeting (who also own the app) were going to be late. Example:
one of your guest is 25 minutes from the location of the meeting but the meeting is in 20 minutes the app would let you know that the guest is running late.

I hope someone would build this. we never did.