From a few years back when Lightning debugging cables were either expensive, hard or not to get at all: [Wayback/Archive] DEF CON 30 – stacksmashing – The Hitchhacker’s Guide to iPhone Lightning and JTAG Hacking – YouTube.
Basically it is a Raspberry Pi Zero with adapted firmware connected to half a lightning extension cable.
A textual description (I wish it was linked from the above video) is at [Wayback/Archive] stacksmashing – The hitchhacker’s guide to iPhone Lightning & JTAG hacking – DEF CON Forums, which in turn refers to:
The Wiert Corner - irregular stream of stuff 