The argument is largely subjective. For one person, making the world a better place is achieved by spending more time with the family to raise good kids that can improve upon their parent's success and keep building.

To others, it's creating something like Paypal or Square.

To another, it's Kiva.

Lastly, as another commenter said, you need money and time. You can buy time with more money, so let's say you just need money. Apps can be used to get that money.