OK, good to know. I'd heard different regarding iPhones and iPads but I don't own one. Perhaps I've been misinformed.
Slightly OT - I know that my Sony PRS650 ebook reader will not work on any kind of external USB supply or AC adaptor. Has to be a PC/MAC or a genuine Sony AC adaptor. I'm told the chargers for PSP will also work with it but don't have one to test.
IIRC, it needs a resistor to be 'recognized' by the iPhone. The stock tip looks the same, plugs into the phone, but doesn't charge the phone. The replacement tip from RS works fine.
The same issue can arise with 'budget' car chargers.
EDIT: This comes with tip #A61
If you want an iPhone tip, it is #A133
Micro USB is #A97
Mini USB is #A32
Interesting, I have a female USB port that is hooked up to just 2 wires. I got it at Radioshack and it does a fine job of charging my phone.
Here is my battery backup:
That’s right. I can charge my phone for WEEKS with this bad boy.
4x 18650 box with 4x Panasonic NCR18650B 3400mAh cells would probably be the king of power boxes - 50 Wh is as much as typical laptop battery, or 10x typical phone batteries! :Р
@Klow, you may want to get one of the 12v to 5v things rather than use an inverter. Those things are extremely inefficient.
@Shadoww, great idea but does anyone know how efficient those boxes are?
Some more info. This as the result of quick Google search. I cannot comment on the quality of the sources but it makes for some intersting reading.
Scaru, how old is your iPhone? It seems Apple have changed their specs several times over the years and many people report the "charging not supported with this accessory" message. Again, I only know what I've read here. But I do know the whole "sense resistor" topic has been discussed in many web forums. Interesting that your phone charges with two simple wires.
If it's a quiet day (night) for you folks, have a look at
http://www.epanorama.net/blog/2010/08/18/apple-charger-secrets/
http://www.ladyada.net/make/mintyboost/icharge.html
and/or
I don’t use an inverter. I use a dual USB charger so I can use my 4Sevens charger and charge my phone at the same time. I have an inverter, just in case.
Subjective test...
The boxes may not be efficient. For s***s & giggles, a few months back I tried charging some Eneloops using the Sanyo USB eneloop charger NC-MDU01. I have the 4 X 18650 with Panasonic 3100s. From fully charged, I managed to use the box to charge 4 AA eneloops. By that time the indicator was showing low charge.
I can't remember what voltage the cells were at but I do recall thinking that either the box or the chargers must be very inefficient if it was taking almost an entire 18650 to charge a AA.
I really just got the box to "store sunlight" from my solar panel but if every joule counts I guess they are not a great solution.
@KLow, that makes sense. :)
Yeah, I have looked through most of those links in the past. I have a 4S and my charger is just a 4S pack of AA nimh hooked up to it. Here a picture is. (Forgive me for the messy hot glue to hold it together)
Nothing messy there mate, just good ol' home-made quality! 
Wonder why it works for you when so many other people are reporting problems?
I'm glad it works for you !
I found another one of the AA chargers, for a total of two - do you want one ?
Yeah, I'm not sure myself. :) I do have plans to 3D print a cover for it but I have to finish making it first.
The 4 AA using 1.2v NiMi = 5 volts
That with some normal eneloops or 2400mAh Turnigy LSD’s is perfect.
Ill ask this guy I saw with one where he got it from.
Ugh... Well after unplugging my phone cord and plugging it back in it no longer works. :'( I checked it at the switch and it still puts out 5.1 volts but now the USB port is dead. It won't charge anything: not my iphone, battery chargers etc. So now I get to peel off the hot glue and test the connections. :P
Jaycar have them here, but as I said earlier they have no smarts or protection of any kind. Pretty much straight wiring with a diode for reverse current protection.
Mine will charge my (older) iPod, but alas, not my Sony reader.
Sorry Scaru, hope I didn't jinx it for ya 
Sorry, yeah we discussed this didn't we - I'm losing track of this thread.
Cottonpickers at CPFMarketplace has a NiMH box something like this I think. David usually sells them as an optional part of his solar kits.
Would be nice to find something more local though.