I've never used that sugru stuff, but saw it online when it came out and figured it'd be useful for just about anything day to day. Must buy some soon! Great tip.
It has two inlays, one is black and the other is transparent. Sometimes you could turn it around, so that the inlay you don't like faces the bottom.
Range varies. If your phone isn't very good then the range will be bad. Note, this has nothing to do with how expensive your phone is. Your phone can be expensive as well as being crap.
Sony make a good phone with a decent range on the NFC antenna.
Yeah, I believe there's a 3D model out there somewhere. Printing in plastic is a whole different scenario - there you're not dealing with the negative effects of nearby metal and so you're not limited nearly as much as you are if you replace the chip/inlay in a metal ring.
If you'd like to have a play around, pm me and I'll get your address to send you a ring with a defective inlay.
You'll have to adhere to the container rules laid out in the NFC specs, and set up an app that will read your nfc ring and inject the text into the place that you want it.
i would use it to store game data combined with the nfc game kids like my free system: NFC Playing Figures / Lego´
where you can make interactive playing systems.