Kali NetHunter is an Android ROM overlay that includes a mobile penetration testing platform. It is officially available for download on newer Nexus devices and the OnePlus One, as well as some Samsung Galaxy models. It also works unofficially on other phones.
Started in 2014, the Kali Linux NetHunter project is the first Open Source Android penetration testing platform for Nexus devices, created as a joint effort between the Kali community member “BinkyBear” and Offensive Security, the company behind the Kali Linux desktop distribution. The overlay includes a custom kernel, a Kali Linux chroot, and an accompanying Android application, which allows for easier interaction with various security tools and attacks. In addition to the penetration testing tools featured on desktop Kali Linux, NetHunter also Wireless 802.11 frame injection, one-click MANA Evil Access Points, HID keyboard (Teensy-like attacks), as well as BadUSB man-in-the-middle attacks. It is based on Kali Linux distribution and tool sets. NetHunter is an open-source project developed by Offensive Security and the community.
NetHunter BadUSB Attack
Enabling this USB mode will turn a device with an OTG USB cable into a network interface when plugged into a target computer. Connecting the USB cable to a PC will force all traffic from that PC (Windows or Linux) through the NetHunter device, which allows the device's user to perform a man-in-the-middle attack. 
MANA Evil Access Point
MANA is an "evil access-point" implementation by SensePost that performs rogue Wi-Fi AP and MitM attacks. The MitM logs get written to /var/lib/mana-toolkit/ in the Kali chroot. Users can change the access point's configuration to match their target environment, such as the SSID, channel number, etc.
NetHunter HID Keyboard Attacks
The NetHunter HID Attacks turn any device and its OTG USB cable into a pre-programmed keyboard, able to type any given commands. It is functionally similar to “Teensy” type devices.