The basic premise of the APP is to aid and assist in the major expenses when traveling by providing an insight to lodging, eating and gas and providing directions to your chosen location.
Tracking your mileage while traveling would alert you to a potential problem if your miles per gallon dropped significantly and verifying the purchase price at the pump prevents you from being overcharged on you purchase.
Reviewing and evaluating the restaurants, motel/hotels, or entertainment facilities, provides a record that you can consult on future travels.