Interesting alternative to spade connectors or old fashioned solder.
I can see the advantages for a folding bike situation with this magnet fittings. Not sure about if I would need on my non folding bikes though. Dynamos and lights are permanently attached with spade connectors on mine so would not need such a quick release for me. If I need to disconnect it would be a 15 second fiddle rather than 1 second as with this fittings, but so rarely need to do it, not worth the trouble.
As for attaching gadgets, that is another matter. Not sure your cable suggestions would alone would be enough. But a cheap USB adapter I tried was ok charging cheap phone, but iPhone wouldn’t charge from it. You need to look through the threads, but there are only a few decent USB adapter that will allow charging while riding reliably. And these were not cheap. If I were planning a tour of several days, worth the investment. But not for daily use where I can charge overnight at home.