Practically, yes. It will reach your subject from there, and even farther - the cord is very long. I don't know anything about the iPhone 5 though, so I can't say that it will work properly with that particular piece of tech. If you have previously recorded through the headphone jack, that it will work fine. The jack is just a standard stereo mini plug, or 1/8" stereo plug.
No. This microphone is a lavaliere or lapel mic and is designed to pick up the voice of the wearer. You will need a 'shotgun' type microphone for what you want to do, or a camera mounted microphone that is designed for wide areas.
Well, it might work if you tape the mic to the top or side of the GoPro and forgo the clip. But, in any case, the mic is just not strong enough to pick up a lot of sound unless it's directly near the source of the sound
I went to Radio Shack and bought a 1/8 plug to 1/4 plug adapter to put on the mic cord. Then I bought a model 274-017 XLR balanced adapter to plug it into a 3 prong mic port. Since the Audio-Technica system comes with a battery/preamp, you don't need a direct box. I plugged the mini adapter into the back of the balanced adapter and the whole thing into the mic port on my Fender amp system. Works like a charm and was suggested by my buddy who runs a recording studio. Just remember to turn the mic off when you're not using it so you don't run down the battery. You'll get very little sound out of it otherwise if the battery is dead. If your system has phantom power, it may work without the battery, haven't tried that yet. Probably spent about $20 total on the two adapters. Good luck!
It will work with a standard 3.5 jack. However, you would need the Audio IN (not out) port on your camera. I don't have that model DSLR, so don't know how it works. However, you could also plug it into a separate recorder (like an Edirol or your phone) and sync the sound afterwards using your video editing software (it is more tedious that way, however).