The quick-disconnect end connects to an identical end on the battery tender cable, which has rings that connect to the battery terminals. I leave mine connected just like that: battery -> cables -> phone, GPS, etc.
You could always buy just the cigarette adapter, cut the end off, and run that to a constant voltage source. The only problem with that, is the other cable actually has an inline fuse, so on the freak chance something goes nuts and draws a crazy amount of power, the fuse blows instead of something much worse happening.
I wouldn't use the horn, because (I could be wrong here), wouldn't you have to press the button to close the circuit and supply power to your charger? I'll probably eventually run mine to either the headlight or the rear running light. The cables are pretty long, and there's lots of places to route them through, so getting to the handlebar area won't be a problem.
I leave mine set up, and just unplug what I was charging.
hey bud, yeah you can do it yourself. You will have to take the wheels off, pretty easy, just follow the manual's directions. It will take about a day of downtime unless you start really early in the morning or you can do it in the evening and then it will be ready the next day. Just follow my "How to plasti dip motorcycle rims" youtube video: