The Mark Mobile Orders add-on flags orders placed from mobile devices with the mobile phone pictogram. The pictogram shows up on the Orders List and order details pages in your store Admin area.
To install and enable the add-on, follow the guides here.
The add-on does not require further configuration. It marks all orders placed from mobile devices with a special pictogram when enabled.
The pictogram displays on the order listing page of your store admin area (Orders -> Orders List):
It also displays on the order details page: