I just finished putting together my own Head Camera Mount, and I have to say that I'm pretty pleased with the result. This was something that taught me a lot and ended up being a completely satisfying project when it comes to how it turned out. I use a Logitech C922x Pro Stream Webcam which gives me some pretty satisfying results when I tested it with Faceware RT. My initial tests identified a couple of weaknesses --I was fine when I was recording in a well lit room during the daytime, and the way that I am when I talk meant that I could not use a deskcam setup in order to facial motion capture. I'm one of these kinds of people who are very animated when I speak so it became clearly obvious that a headcam was the only way to go for me.  The only problem was that people seem to want an arm and a leg for a headcam rig which quite frankly bothers me. So I set about the task of creating my own. I did not want to spend and arm and a leg and I didn't want to purchase a new camera when I already have gotten this one setup and I'm comfortable with it.  This is what I came up with:

Thanks for posting, as I think this will be of interest.

So what is the part that is attached to the helmet? Looks like some sort of gooseneck for a camera?

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I was never too interested about something like this until yesterday, when I got all excited (and still am) about the iPhone X Live capture.  And, like you, this might solve a lot of problems for me as well.  

Naturally it will be a LOT simpler -- for one thing, it can be wireless, and I really just need the mount part -- but I still need to work on the details of attaching the arm to the helmet (the tricky part).  And with the iPhone I won't have to worry about lighting, either (it works even in an almost completely dark room, since it uses infrared).

So share any of the deets you want -- I'll certainly be interested.

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Alienware Aurora R12, Win 10, i9-119000KF, 3.5GHz CPU, 128GB RAM, RTX 3090 (24GB), Samsung 960 Pro 4TB M-2 SSD, TB+ Disk space
Mike "ex-genius" Kelley

For the iPhoneX Profile, all you need is something like this that you attach to a helmet.
https://www.amazon.com/ZTON-Universal-Bracket-Flexible-Bedroom/dp/B01H8RDAX6/ref=pd_lpo_vtph_107_lp_t_2?_encoding=UTF8&psc=1&refRID=9AHHQQPSNXQSA8E66K1C

I don't think so, Rampa -- most of the reviews I read of "flexible" arms for phones said they weren't any good due to vibration and motion, something you would NOT want for this.

I think it almost will have to be a rigid arm thingee, but I just haven't found anything really suitable yet.

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Alienware Aurora R12, Win 10, i9-119000KF, 3.5GHz CPU, 128GB RAM, RTX 3090 (24GB), Samsung 960 Pro 4TB M-2 SSD, TB+ Disk space
Mike "ex-genius" Kelley

The mounting arm is a 27 Inch Gooseneck Mount by AceTaken. I chose it because it had all the pieces I needed to mount everything on the helmet. I even reused the clamp itself, drilling two holes into it to use it as the anchor point to the helmet. You can disassemble the clamp, drill two holes in it and then mount it on the top of the helmet. Just make sure you pick a helmet with a hole in the top  so the bolt that holds the arm in has somewhere to sit.

It's not complicated to mount the connector to the top of the helmet. Drill two holes and voila!

I'm not really big on the iphone X. It just seems kind of silly to buy a $1000 dollar phone just for one feature. The whole point of this undertaking was not to spend a lot of money. As far as cell phones go, I'll never purchase another iphone --being an Apple customer left me traumatized and I've no desire to be at their mercy again. What I found when it comes to articulating arms is that you have to find one that is going to stay the way you pose it, and the mount has to have as very little play as possible. I don't really have any intention of trying to do intense motion caption --I just want to be able to move my head while I'm recording. It's stable enough for my purposes. 

I certainly wouldn't buy the iPhone X for this -- but since I already HAD the phone using it for this is a no-brainer, particularly since early reports are this is MUCH better than Faceware (which I own as well).  And, truly, it's the best phone I have ever owned, and I've owned cell phones for three decades now.  It truly is the phone Apple should have released two or three years ago, perfect in every way.

And this application?  Icing on the cake.

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Alienware Aurora R12, Win 10, i9-119000KF, 3.5GHz CPU, 128GB RAM, RTX 3090 (24GB), Samsung 960 Pro 4TB M-2 SSD, TB+ Disk space
Mike "ex-genius" Kelley

I think it is actually a pretty good reason to buy an iPhoneX. It's not like the alternative is whole lot cheaper, and this a complete wireless solution. There is also a possibility of doing your body mocap on the phone at the same time. Granted, that's not cheap, but not that outrageous either.
https://wearnotch.com

Imagine a mocap studio in your pocket, and it starts to look pretty good!

Many helmets use rigid rails or a rigid arc off the top. There are certainly lots of DIY options.