There'll be 2 kinds of users in it.
This person got excess food at his place. So he will open up the app and notify that he got some extra food that he's willing to give away. He'll post what kind of food it is and with a photo as proof.
This user get's notified that User1 who is this much km from your location want's to give away some food. Then this user will accept it and he'll get the location of User1. User1 will know that this User2 is on the way, with a live tracking system. I'll prefer cyclists as User2 because it won't cost anything and it'll be a promotion of cycling also.
Now when User2 reaches and collects the food, he'll give User1 a badge or something as a respect. Then User2 approaches and gives it to some homeless/hungry person on his way. User2 clicks a picture and User1 will see that it got reached where it needs to.
Now, these users will be listed in the app leaderboard. For User1 it'll be the number times he gave away food, for User2 it'll be the Kilometers he drove.
It's not necessary that the food must be extra food that he doesn't want, he can prepare food just for a give away also. And it's not necessary that User2 should be on a bicycle.
That's how it'll work. I need opinions on chances of failure, or improvements on this idea (see issues). Thanks.