[bradbatt]

How about just require a photo upload and then look at the photo's metadata (time, date, GPS, etc) to match it up with the data they already have (i.e. where the driver is)?

Maybe built in the camera directly into the app so that the drivers don't have the ability to fake an image's metadata.

[tuesdayrain]

Any bulimic fraudster would have no issues supplying dishonest "evidence"