As the name for this case implies, TuneWear’s Prie Ambassador SideHook has a hook along the right side of the case for latching on to a belt loop or bag. It’s a strong metal hook that uses a spring to keep it closed; you don’t have to worry about the hook failing, but since the case offers no face protection, I’m not comfortable letting my iPod touch dangle from my backpack. The hook, which also doubles as a horizontal stand, is removeable but the nylon loop to which the hook attaches isn’t (though it never got in the way during my testing). I actually prefer to use the case without the hook, and the case isn’t overly bulky; your encased iPod touch won’t feel too big in your pocket.
The back of the SideHook has a little card pocket that can be handy for storing the proper items. I advise against putting any cards with a magnetic strip into the SideHook’s pocket, however; the iPod touch creates enough of a magnetic field itself to render the strip useless. (I speak from experience; I’ve had a few BART tickets and MUNI bus passes negated because I kept those cards too close to my iPod touch or iPhone.)