Apple has drawn some serious criticism lately for their strict policy on App Store approval which has led to a number of seemingly random rejections. Apple has not only been rejecting applications that compete with their own, they also forbid companies from using undocumented APIs to develop them – supposedly because they are often in active development and subject to change.

Google’s voice search function on the latest version of its Google Mobile search app, however, appears to break the rules. The company has admitted using the undocumented proximity sensor API in order to add a nifty feature, which allows the phone to sense that you want to conduct a verbal search when you put it up to your ear and then performs the search when you move it away.

Apparently the occasional use of undocumented methods in public iPhone frameworks is not that rare in third-party iPhone apps. Now that Google has come clean, though, Apple might choose to enforce the rules of the iPhone SDK and force the search giant to rewrite the application – or at least alter the way it utilizes the proximity sensor. Then again, if it doesn’t, it might set a precedent of favoritism.