There is a project (iphonebluetooth.tk) to unlock the iphone bluetooth. The developers got some interesting progress. They were able to search and find two other bluetooth devices (a sonyericsson phone and an hackintosh) from the iPhone, and transfer some data. Here are several interesting screenshots:
TyroTuner is a microphone-based utility that tunes the standard six-string guitar. Select what string you want to tune, and then play the guitar string...the needle will tell you whether you need to tune up or down.
The application costed $2.99, but it is now free for a limited time. Here is the AppStore link.