I'm Hugo the owner of Rydon and came across this post, and thought I would give a little background information. Rydon is based in the Netherlands, were cycling is part of our daily life, we have actually more bicycles than people in the Netherlands. I cycle everyday and got frustrated with the lighting, so wanted to design a Bicycle light that simply always works. This was the start of the Rydon Pixio. I have seen a lot of comments about the light output, the light is developed to be seen rather than to light to road. If you need a light with a lot of output to lighten the road up a head the Pixio is not for you, if you like urban cycling and need a simple care-free light so you are safe in traffic the Rydon is perfect.
Our claims regarding the 75 hours and 2 years is based on Dutch numbers and I understand that people use their bicycle differently over the world, it was also quite confusing so we changed it. We have produced the lights and made some small changes from the original design. For example we charge the batteries for 65% instead of the 100% which we did during testing. Fully charged the light will shine for at least 60 hours straight. If the Pixio is in full sunlight the light will charge the batteries with about 50-60 mA, the light consumes 20mA. The batteries we use are low-self discharge so they hold there energy for longer periods of time. If you have any questions regarding the Pixio please feel free to contact me.
Of course, if you're willing to have an easily stolen 1.5 sq ft solar panel hanging off of your bike, then sure, it'd work wonders.
I've been wanting to fasten a flexible panel to the back of my jersey to charge a battery pack. If it was cheap yet I'd do it, BUT there is a big problem in the concept. If I'm charging for lights, I need that in the winter but I'm commuting in the dark or twilight then, morning and evening. There might be two months where I could both charge it and still need it. If I want it for phone or tablet on a tour that would be great, but the last time I toured was ... never. So the whole idea is just a lark for me.
This is not a new idea. I had a solar powered Planet Bike light as a gift - the solar panel was integrated into the light. It was also underpowered and pretty useless, even only as a "too be seen" light (and even on backup battery). I think the only light that helps you to be seen is very bright and flashing.