I've made a few headset adaptors recently, seemed worth sticking a note here so I can work out what they do later.

This one adapts a cheap four pin phone headset to the FT817 (and probably similiar rigs), and adds a toggle switch for PTT. Used to good effect in the 2m backpackers contest last month, after a wrap with insulating tape:

And this one adapts a kenwood-style 2.5 + 3.5mm headset to two 3.5mm plugs to use with my ubitx:

Both liberally potted with hot glue...