Yes, the B&M Cyo was a watershed, as you say, Martin, the point at which bicycle lamps achieved their adulthood. I too wouldn't be without the stand light function.
There's also an auto-on/off light-sensitive switch on the upper-level B&N lamps which someone with a device charging requirement might consider useful.
I don't charge my phone from the dyno on my bikes -- instead I have a small lipo backup which fits in the handlebar dry bag for the iPhone which puts my heart rate directly in my sightline, and either the lipo or the phone directly can be recharged from my bike's electric motor battery, just a matter of plugging in the cable, which is carried on the bike, so the phone always returns home fully charged, however long the journey.
However, I had an experience a couple of years ago which gave me to grasp that the light-sensitive switch might be useful in a dyno-device charging/recharging situation.
Normally, when more than two or three people cycle with me, we agree where we're going and I ride in front with whoever wants to talk. But on this day I was bringing some stragglers along through town at the end of our countryside ride, and the rest of the group was before us on an unavoidable inner bypass at a point where the stem of a T junction comes into it, carrying an entire region's bus and lorry traffic among the cars. The building facing this T is the back of a church with a very few windows high up.
The minute the lead group of cyclists disappeared into the shadow the church cast, they were just gone. And this was on a bright sunshine day, and even though I wore prescription polaroids. It wasn't until a cyclist wearing a reflective Sam Browne belt rode through a beam of light cast by a stained glass window that I picked them up again. A driver in a car or a truck would have the same difficulty in seeing even several cyclists in that high-contrast shadow, as several confirmed by flashing their lights immediately the sunlight shone briefly on the Sam Browne to establish for themselves that there was something on the road under the church. I returned after we dispersed at my front door, less than a kilometer beyond that and parked my bike behind the back of the church, and the rear lamp (B&M Line Plus) definitely made it visible from a distance, and so did the broken Sam Browne I use to stabilize the bottom of the pannier basket.
Riding through that section again and again with various switch settings for the lamps, and later riding in the countryside through tunnels of trees or deep valleys, I discovered that the light sensitive switch will recognize situations like that and switch the lamps on. We don't have any except a short disused car or train tunnel around here to use for a test, but a tourer might meet tunnels as well, and cities are not called the "urban jungle" for nothing. These are all good situations in which to know your lamps will switch on as necessary until you come out into the light again, when they will switch off again, and the dynamo will resume charging the batteries in your other devices.
iPhone owners may have to be a little careful with this facility. Apple is awfully finicky about the level, quality and constancy of power used to recharge their devices, which is why I like having a buffer battery between my iPhone (and expensive electronics in general) and the power source. I did however try charging my iPhone 4S from the SON via a DIY charger built on a USB output board I bought in China, and it charged fine regardless of interruptions to redirect the power to the lamps. Unfortunately I gave the board away or broke it up for parts or just lost it because when I replaced the 4S with an iPhone SE (2016) and wanted to try it on that, I couldn't find the DIY bike charger. Too bad, but no reason it shouldn't work on the 2016 SE as well, or the current 2nd generation SE first seen in 2020. Part of the reason I chose the iPhone 4s and the SE is that they have superior heat dispersion through the carved solid aluminum body and can thus be left on and operating, recording my heart rate and recharging at the same time, for hours on end. This is relevant because I suspect that the root cause of Apple's finick with the quality of charging devices is inspired by not wanting to spend money developing and building in a proper amount of heat dispersion and thereby adding bulk and mass to their elegant phones which, if my suspicion is right, makes it logical to conclude that Apple software uses battery temp as the main switch in charging shutdown. This is also the reason that the generality of bicycle dynamo owners hoping to charge especially Apple devices, but possibly others too -- I don't know, should buy a charger from a reputable maker rather than trying to DIY their own: that the reputable maker's device will put out clean power, meaning a constant current which in turn guarantees the tightly specified voltage Apple demands.
