A small bridge board to link a programmer to a PCB, via a card edge connector. See debug-edge.io for more the full specification and rationale.
A nice, easy to use debug/flash probe adapter that can quickly and easily connect to a board, staying put as you need it!
Greg Davill mentioned coming across the AVX Open Ended Card Edge connector, and Scott Shawcroft followed up that it'd be a good idea to explore a conversion from a typical 10-pin SWD/JTAG connector to the card edge format.