But, my iPhone will hold a change for more than a day, so I'm not sure I'd need it for that.
Your phone may hold a charge for a day under normal circumstances, but if it is the only communication device you have, you may be using it more. The phone also may be running at a higher power level (therefore using battery faster) if some of the local cell towers are not available. As for one day being enough - check your fav search engine for how long power was out after Hurricane Sandy.
Tip - In emergency situations, avoid voice communications, use text msgs. Your device power will last longer and you may be more likely to get through since SMS uses less bandwidth.
1. I've seen lots of mentions of using this with iPad 2/3. What about the original iPad? any reason it wont work with that (Is my iPad an antique??)
As long as the device will charge from USB these devices should charge it. Perhaps slower or faster depending on the output of the port on the uNu device you are using. (Yes, your iPad is an antique, as long as it still works, who cares? With care, the battery is probably the first thing to go, so this may actually extend its life.)
2. Can I use my device while it's connected, or do I use this to recharge, then use the device? ie: in the blizzard, no power, ipad down to 20%... can I hook up to this and watch my movie while it's charging (or at least connected), or do I have to wait until it's recharged?
Plug your device into your computers USB port and start it charging. If you can use the device while charging from your computers USB, it should work the same way with the uNu pack.
3. any reason I couldnt use this ON an airplane? any FAA rules that will cause the air marshals to tackle me in the isle for using illegal power devices?
According to the FCC there are no reasons you shouldn't be able to use most electronic devices on planes anyway. http://www.nbcnews.com/travel/travelkit/fcc-urges-faa-rethink-electronic-devices-planes-rule-1C7500898
As for whether any given planes electronic device compliance bonehead (woot won't let me use the right word) will tackle you for using this - they shouldn't - it is simply a remote battery pack. If you are allowed to use iPad/ MP3 players at that stage of your flight, this device is good to go.
4. What do others use them for? camping? long car trips? third world airports? zombie apocalypse?
All that and more. Especially the Zombie Apocalypse.