NetX PRO [Android] FREE (Usually $3.69)

Looks like a basic network tool app for android - similar to Fing. I haven't used the app personally, but it seems to have some positive reviews - currently rated 4.7 / 5 (802 reviews). Also, I'm not sure how long it will be free.

App Description:
- Network scan: discovers all devices connected at the network.
- Displays most important information for each device connected, IP Address, MAC Address, Vendor, Bonjour Name, NetBIOS Name and Domain.

• Wake On LAN (WOL): switch on a remote device from your phone or tablet when you are connected via wifi or with a mobile data connection.

• Secure SHell (SSH): put a remote device in sleep mode or shutdown from your phone or tablet when you are connected via wifi or with a mobile data connection.
  Displays the operative system version installed on the remote device. (In the remote device must be installed and started a SSH server)

• Loads off-line all devices of a network previously detected.

• Adds a new network or a new device manually in order to manage all functionality for a no detected device.

• Shows information about the wifi connection (external IP, signal strength, download and upload speed, subnetmask, gateway, DNS).

• Shows information about the mobile provider (external IP, signal strength, download and upload speed, CID, LAC, MCC, MNC).

• Wifi scan: find nearby wifi and displays SSID, signal strength, channel, encryption.

• Shows graphically the band width and the overlapping between channels of wifi networks.

• Monitoring and diagnostics remote devices: shows CPU usage, RAM usage and displays the available memory inside the disks.

• Monitoring access to network wifi. Receive notification when a new device or an unknown device connects to the network.

• Ping functionality. It's possible to ping every device connected and any hostname or IP Address.

• Port scanner to scan the most common port used.

• Themes available.

• Available languages: Czech, German, Greek, English, Spanish, French, Italian, Dutch, Polish, Portuguese, Russian, Turkish and Chinese.

• Traceroute shows the route of packets that are sent from the smartphone to target host. It's possible to see the route also on the map.

• IP calculator: this tool calculate the network parameters like netmask, CIDR, ip address range hosts number etc…

• IP location shows the position of the IP address on the map.

• MAC address lookup allow to get the vendor from MAC address.

• DNS lookup allow to get the IP address of the domain, mail server etc. Reverse DNS is supported.

• Network position shows the position on the map of the network scanned.

• Backup/Restore data on the local folder or with google drive.

• Speed test: this tool calculate the download speed and upload speed.

• Supported tethering mode

• IPv6 supported for Ping, Traceroute, Port Scan and IP Calculator