I suppose this is more practical than the Lightning-to-1/4" phone plug adapter I instinctively built when I noticed Apple's headphone adapter fit comfortably inside a run-of-the-mill 1/4" cable-mount jack (of the sort found on the sink end of a headphone extension cord).
I've also idly considered doing the reverse with one of my iPod shuffles, i.e., incorporating the shuffle electronics into the shell of a 1/4" connector; trouble is, the shuffle runs USB through its four-conductor headphone jack, and 1/4" TRRS connectors are thin on the ground (AFAIK the 1/4"-ish TRRS aviation jack is physically incompatible with ordinary headphone plugs).
I've also idly considered doing the reverse with one of my iPod shuffles, i.e., incorporating the shuffle electronics into the shell of a 1/4" connector; trouble is, the shuffle runs USB through its four-conductor headphone jack, and 1/4" TRRS connectors are thin on the ground (AFAIK the 1/4"-ish TRRS aviation jack is physically incompatible with ordinary headphone plugs).