I've just bought an
Inka keyring pen, and these are my first impressions. Conclusion: I liked it. This picture is from Inka's site:
See their site for details of construction, etc, as I'm not going to repeat that stuff. I'll mostly compare it to the classic "bullet" Fisher Space Pen.
I find the "quick-use pen" can be too small to be comfortable. It's like writing with a pencil stub - it's less than 3 inches long.That's about 3/4" shorter than a bare Fisher Space Pen. It's much better than a naked Fisher refill, however, and much better than the tiny pens you get with some Vic Swiss Army Knives. Some practice helps to figure out how to hold it - it's too small to hold as a pen, but you can jam the end into your palm to stablise it, or angle it up so it lies closer to your finger knuckle.
The "full-size pen" is fine for writing with, but can be a bit fiddly to assemble. It's not like pulling a pen out of your pocket and using it. Nor is it as easy as taking the top off a Fisher Space Pen and putting it on the end as an extension. You have to unscrew two pieces, screw one in and push in another. When you do that it becomes 5" long, which is great. Shorter than Fisher pen with top, but easily adequate at least for my average-sized hands.
When stowed the Inka is shorter, thinner and lighter than a Fisher, but still not really small enough to go in my wallet. It really belongs on a keyring. Build quality is good. The design is good generally - there's no wasted space and I can't see how I would improve it, given that it needs threaded connectors for strength and security. I have no fear of it falling off the split ring. I've not tested the water-proofness yet. When you take the inner pen out you get a hollow tube which you can use as a (very) short straw, or as a small water-proof container/pill-fob that would in extremis hold a few matches, but with the pen stowed there is no spare space. Not even for a scrap of thin writing paper.
So far the writing quality of the nib has been good. Fisher pens are prone to ink "globs". I've not seen any globs from the Inka despite it using similar pressurised ink. I'd be interested in comments from other users about this. It seems to write as well as a Fisher on wet paper, upside down etc.
The PDF stylus seems like an after-thought. As far as I can tell it can only be used in "quick use" mode. I suppose it's better to have than not, but it doesn't make much difference to me.
I got the $25 model direct from the Inka website, which included postage to the UK. Some other vendors wanted to charge ridiculous postage. I'm not sure I'd bother with the $90 titanium version. Delivery took just a few days and the package is small enough to go through a letterbox, so no waiting at home for it or stupid import duty to pay. (These things can be a pain when ordering American stuff from the UK.)
Although I've mentioned a few negative points, overall I'm pleased with it. It's an every-day carry pen. It's the first solution that has actually worked for me. I am finding I use it nearly as often as I use my EDC torch or knife, and much more often than some of the other stuff I carry around. Now I just need a girl to give me her phone number so I can write it down quick. I'm sure she'll be impressed.