This is interesting. Today, the US Patent & Trademark Office has released a patent application from Apple in 2010. The patent application details a process to unlock your iOS Device by recognizing your face and/or your presence. Facial recognition security has a few potential flaws which may have prevented it from being implemented before. Namely, lighting and shading. Most facial recognition software is either created to handle lighting or not to handle it, with the former requiring much more processing power of the two. Therefore, being able to handle lighting has negative affects on both the processor and battery of the device.
The even more fascinating part of this idea is that Apple may plan to handle the potential resource drain by not matching your entire face. Instead, a reference image will be used for the common aspects with the higher information areas (eyes, nose, mouth) being added in from a picture. This may reduce processing needs and save both precious battery and processing power. Of course, this is only a patent and may be filed only as a deterrent for other businesses who may use the idea. Nevertheless, it is interesting.