SIMable is an "ultra thin chip" that you attach to the SIM card of your choice. It's not a simple matter of slapping it on, though. You have to align some things up, use a scary-sounding machine called the cutting press, poke some holes into the SIM and make sure the stars are all crossed. Once that bit of magic is complete, simply insert the paired chips into the cell phone of your choice, and voila, one unlocked phone.
24/7 Mobile Solutions notes that, "Whilst mobile phone unlocking is not illegal, it will, in most cases, invalidate the handset's warranty. SIMable requires no handset interference and thus the full manufacturer's guarantee remains intact. The company are keen to stress that unlike any other similar application on the market, SIMable enables 100% functionality on all phones, including full 3G operation."
Nice to know SIMable isn't going to screw with your phone's warranty. Since you're not actually altering the software of your phone, it isn't voided. And it's also nice that the phone will retain all of its features. Sometimes, when you unlock phones, they will lose carrier-specific functions. If you chose to remove the paired SIM cards, the phone will return to its original, locked state with no one the wiser.
You can order SIMable directly from 24/7 Mobile Solutions here. Happy unlocking!
P.S. -- This won't work with Verizon Wireless or Sprint phones, as they don't use SIM cards. Also, AT&T, T-Mobile, and other carriers will likely unlock your phone -- if it is locked at all -- for $20 if you take it to a store and ask. If you go that route, however, your phone will be permanently altered.