Apart from fingerprinting that has already been mentioned, a relevant article: “ACCessory: Password Inference using Accelerometers on Smartphones” http://www.hotmobile.org/2012/papers/HotMobile12-final42.pdf

“We show that accelerometer readings are a powerful side channel that can be used to extract entire sequences of entered text on a smart- phone touchscreen keyboard.”

Pending research to the contrary, I would assume that what is typed on the keyboard of a laptop can be recovered through the accelerometer by an application running in the background.