Unlocking a 3G iPhone is hard. The best efforts of the iPhone Dev Team have not yet produced a software unlock, so if you really want an unlocked iPhone, then you have two options:
1) Buy a legally unlocked iPhone from Australia – with a premium of at least £200; or;
2) Use an unlocking SIM card.
The second option is trickier but does mean that you can buy a PAYG iPhone, and use it with whichever carrier you want, without having to pay the unlocking premium.
A little while ago, Solutions Point released the Rebel SimCard, and they sent me a unit to review. Here’s how it went.
The basic premise of their offering is: No jailbreak is required. All you have to do is insert the unlocking card over the SIM you want to use, slip it into the iPhone’s SIM tray, and the iPhone will be fooled into thinking you’re using the SIM of an official carrier (it does this by faking the IMSI)
It’s billed as “The World’s Only Solution to unlock iPhone 3G”, which isn’t strictly true. There are a few of these unlocking SIM overlay cards around, e.g. the Tornado SIM.
Cost: £10 gets you the Rebel SimCard, or £15 if you require the cutter (you will) for the carrier SIM that you want to use.
Sounds simple 
Testing
I took out my O2 SIM, and grabbed a PAYG Orange SIM that I had lying around. I had to cut the Orange SIM a couple of times, but eventually the Rebel SimCard fit snugly over my Orange SIM.
Ok, here goes. I inserted the SIM tray back into my iPhone 3G, and waited… and then the Orange name popped up as the logo. Job done! It was that easy. “Great”, I thought, “I’ll take that out now, put my real SIM back in, then put the Rebel SImCard back in tomorrow to properly test it”.
Tomorrow arrived (as usual) and I swapped the SIMs over again. It took a little longer this time as the Rebel SimCard had slightly turned up at the corner, and didn’t slide in quite so smoothly. On to testing. Calls and texts in and out worked fine. Wifi was fine (as you’d expect), but unfortunately, 3G and any mobile data were not working. That is going to be a deal breaker for many, as it’s the 3G iPhone.
Testing ended, and I came to take the Rebel SimCard out. It would not budge. Oh dear, this is bad. In the end, it took me two hours to remove it, using needle-nose pliers and a fair bit of profanity. It came out but I broke the SIM tray a bit.
So would I recommend it?
That depends.
If you’re buying a 3G iPhone for the 3G data, then you’re out of luck. Solution Point told me that they’re working on it, but it doesn’t provide a 3G service right now. I would also not recommend it if you’re going to be swapping SIMs often, as you run a high risk of physically damaging your phone. There’s also the issue of the IMSI faking, which is discussed at length in this Hackint0sh forum post.
However, if you’re only going to insert it once, then it should be ok. It does provide you with the latest iPhone unlocked to any GSM network. YMMV.
STOP PRESS: Just as I was about to post this, I noticed that Pocket Lint are reporting you can now buy an unlocked iPhone direct from Apple in Hong Kong. It’s £375 for a 8GB iPhone, which is only £25 more than a PAYG version from O2 in the UK (excluding shipping).
UPDATE: Solution Point contacted me and said that they’ve updated the Rebel SimCard firmware twice since they sent me the review copy, and that it now works with 3G.