A company called SIMable has produced a little chip that they call the "10-second solution" for unlocking carrier-tethered GSM handsets. The gimmick is that, instead of unlocking the phone itself—and risking invalidation of your warranty— the chip works on the SIM card, provided you punch a hole in the SIM.
Yes, I said "punch a hole." The SIMable card lies flat against the SIM, and you first have to perform the following surgical procedure. At least the hole-puncher comes free with the £16.99 chip:
It's not clear if SIMable is shipping to the US, though there's no reason to believe it wouldn't work here. There's also no mention of Apple's iPhone on the site, although the Inquirer mentions it in the first paragraph of their own writeup. Hopefully SIMable is just getting around to that, after testing on 70 or so other, more popular phones.
Update: Corrections were made to the post following some clarifying comments (thanks!). As far as this being a copy of other products, that may very well be the case, although SIMable maintains that it is not:
NOTE - SIMable is not linked in any way to other similar products and enables full 3G functionality. We include a free customised cutting press ruling out any messing around with scissors.