Just tried it out, and it worked - I pushed the .apk to /system/apps, started it up and hit the button, the row of lights at the bottom of the phone blinked several times, and then, voila, the code appeared. Put in another SIM, entered the code in, and it unlocked phone. I confirmed that the phone was unlocked after I put my T-mobile SIM back in.
The only thing is that my call logs and favorites were wiped out. I have no clue if this minor side effect is part of the unlocking process or is related to the app/script.