Researchers from MIT and Georgia Tech have developed a new technique that enables them to use the accelerometer in an iPhone or other smartphone to capture keystrokes from a nearby PC. The tactic, while quite complicated, could be used to conduct password-recovery or other attacks on unsuspecting victims. The research relies on the fact that the accelerometers in modern smartphones have become sensitive enough to detect the vibrations produced by someone typing on a keyboard a few inches away on a surface such as a desk or table.
Source: https://threatpost.com/new-research-shows-possibility-using-iphone-keylogger-101811-0/75768/