If you would like to know if neighbours are using your Wi-Fi, Fing can help. The app quick shows a list of all mobile phones, tablet, computers and other devices connected to your current WiFi network.
The device’s MAC address is shown in the list but since that can be confusing, it also shows the vendor’s name and an icon to quickly help you identify devices.
The app also features network tools like Ping and traceroute to troubleshoot your network and discover bottlenecks. There’s DNS lookup and reverse lookup as well to help you figure out if the network has issues connecting to a particular website or IP address.
One more thing. You can enter the IP address of an external network and the Fing App will scan the various ports that are open and accepting connections.
The app is free and a much better alternative than remembering complex terminal commands.