The Kong Cable is a JTAG/SWD Cable capable of debugging CPFM 00 or 01 devices (EVT and DVT devices) which have the Lightning port, using software called Astris. It can do JTAG/SWD and UART/Serial. They can be purchased from obscure markets.
Uses
Dumping the SecureROM
One use of the cable is dumping the SecureROM from devices. This can be done using commands such as this one.