This is one of the best earning method through your smartphones. You take high quality images of nature, places, people, things, buildings, cars, mountains etc daily through your smartphones, but you can also sell them online too and earn money from it.
Whenever someone likes your photo and willing to buy, he/she will pay you first the price you have set for that photo. You can also get paid multiple times for one photo
Following are few sites to support you in this field