In the hands of motorists, smartphones can lead to car wrecks. They also can reduce the hassle of a post-accident repairs. Using an app called Snapsheet, drivers can photograph their damaged vehicles and send the pictures to Snapsheet's team of appraisers, who work with auto insurers including USAA, MetLife and Hartford to speed things along. Newer tools include a payment processing system, an app that helps salvage yards assess the value of totaled cars and a network of specialized appraisal photographers for insurers that prefer third-party images.