Thanks for that @Simon, it just goes to show that mileage really does vary between individual devices!
I also have a Nexus 5, and I've been running a QA failed SB for around a month now as a day-to-day unlock ring: it sits on my finger 24/7 and I expect it to unlock my Nexus 5.
To begin with it was very hit and miss and for maybe 2 weeks half the time I'd give up in frustration and just use the PIN, or swipe on the tag in my slip case. With time though I've learnt:
(a) it is very sensitive to the tag being square on my finger. If the ring has rotated even a couple of mm it makes a read impossible. Fortunately my SB has now had some wear and the underside of the metal has some bare metal where the plating has worn off, so I can tell which tag is 'down' and whether it is in the right position.
(b) my sweet spot is small and can benefit from a slow movement of the ring through the field if I don't get an immediate read.
(b) Rings works best at a 45' angle (i.e. tag not horizontal or vertical to horizontal axis of phone, but at 45'). Fortunately I wear the ring on my left index finger and so it is easy to hold the phone in my left hand with the ring on the exact spot and at that angle without effort.
Now my success rate is probably around 95%, and I don't often need to reach for the emergency tag or use the PIN.
@shama yea, sounds good. We still need to address the issue of "proximity" IE you don't need to use your ring to unlock your phone if you are using sat-nav or if you at a trusted WiFi spot but those are V2 things. Initially just learning about interactions is a huge step forward for the project so thanks for sharing and keep up the good work!
Fingers crossed something lands in AOSP soon.....