In some implementations, a method performed by data processing apparatuses includes receiving, by an item verification engine, a scan notification indicating that a mobile computing device has scanned an item. In response to receiving the scan notification, the item verification engine provides an instruction for a cart computing system to activate item sensors on a shopping cart. The item verification engine receives sensor data collected by the item sensors as a result of the item having been placed in the shopping cart. The item verification engine receives item verification data for verifying the scanned item from the mobile computing device, performs a verification of the item based on the sensor data and the item verification data, and provides verification results for presentation by the mobile computing device.