There's only one headphone I know of, the Precide Ergo, that uses an AMT for each driver. There are dynamics, multi-driver dynamics (new JVCs and I think some of the "surround sound" headphones), BAs, electrostats, and planars, and although I'm not aware of any production models I know some people have done DIY ribbon headphones.
 
I personally like the Air Motion Transformer technology. Love might be a better term. I'm trying not to be tempted to buy the Adam Audio Column MK3 Active, which uses a high frequency AMT as well as a mid frequency AMT down to 800 Hz. I had ESS Heil AMT-1s when I was a kid and now have Emotiva airmotiv5s for my desktop system. I like the airmotivs, but the crossover is at 2700 Hz so a significant portion of the midrange is being handled by the cone driver. The Adam Column is really the only readily available, production, decent speaker I can find that has an AMT working deeper into the midrange and an active crossover / separate amp for each driver (if you know of others please let me know!). Unfortunately at $10,000 it's about 3.3 times as much as I want to spend. Also wish it was a dipole (like the ESS).

But enough about me. AMTs are popping up everywhere these days (patent expiration? neodymium magnets? modern manufacturing techniques making it easier to create the diaphragm?), but usually crossed over in the 2500-2800 range like my airmotivs. But maybe it's just a matter of time before a more affordable midrange-AMT-equipped speaker hits the market. But with the new prevalence of this technology in speakers, where are the AMT headphones? The technology would seem to be a natural for headphones. Efficient, very fast, rugged. I would love to hear what AMT bass sounds like...
 
Thoughts?

I think the difficulty lies with creating a full-range response out of a single AMT driver. Most of the speakers you mentioned probably put their crossovers at the higher value because the AMTs used were unable to produce those lower frequencies as well as conventional dynamic cone-drivers. As a whole though, I think the AMT technology is extremely effective at reproducing high frequency information, and is an almost ideal compromise between electro-statics and pure ribbon sound.
 
As far as developing a headphone around AMTs, one may be able to tune the bass using a ported or semi-open design. In fact, since the driver primarily rapidly compresses air to make sound, these may even be a perfect candidate for a mid-sized entirely closed design. In that case, one would not have to worry as much about an internal pressure limiting excursion of a diaphragm. (the pressure adjustments might be the key to coaxing some serious bass)
 
Maybe if someone could locate a reliable and cheap source of smallish AMTs, mods and testing could begin...