It comes with a cheesy keychain that is easy to remove. Also it easily comes apart into two pieces. The battery end with the green power LED has a male DC adapter end. The iPod dock connector part fits over that.
As an "emergency charger" this thing fails miserably. I connected a brand new store brand alkaline 9-volt battery to my iPod which I had run all the way down earlier by playing music at 50% volume and no backlight. The iPod booted up without a problem and the charge indicator was moving regularly as the iPod charged. I went to the playlist I had set up for the test and began playing music. Within four minutes the iPod stopped playing and had frozen up (the buttons made a clicking noise but didn't do anything; I had to force a restart by holding the two middle buttons down). The charging indicator was moving erratically, I believe between charging and not charging (when the battery voltage drops below the threshold for charging the iPod, the iPod stops charging, which allows the battery voltage to go back up, and the iPod tries to charge again). I disconnected the charger and the iPod played for 40 minutes. I connected the charger again and, upon startup, immediately started getting erratic charging. So I disconnected the charger again and the iPod shut down from lack of power almost immediately. None of the parts ever got hot during the test.
Newer iPods draw less power than my third generation iPod so I can't say that it wouldn't work on 4th and 5th generation iPods as well as Minis and Nanos, but it was a complete failure with mine, like pulling a boat with a moped. Also commercial 9-volt chargers work better on a partially charged iPod, so it might help extend the battery time before the internal battery dies completely. The erratic charging and freezing up the iPod can't be good for it. The brand new 9-volt battery out of the box measured 9.59 volts. After the very brief charging cycle of a few minutes, it measured 8.63 volts (still good enough to use in most devices) and eventually recovered back above 9 volts again. I wanted to see how much power the adapter itself used so I removed the dock adapter and measured the voltage at the DC tip measuring a drop in voltage of only .03 volts. So it certainly doesn't drop the voltage by much on its own.
WARNING: Because the battery pack has the positive and negative so close to each other, when the pack is not in use a battery should be removed. If anything metal shorts out those two ends it could cause a fire (a plastic cover would also work). Also it isn't advisable to leave the battery pack connected all the time; instead use it to recharge the iPod for up to an hour at a time.