Device is a noun. Devise is a verb (with rare exceptions). The noun has a few definitions; it can refer to (1) an invention serving a particular purpose, (2) a technique, and (3) a literary contrivance. To devise is to form, plan, or arrange in the mind. So one might devise a device—though the words are not often closely associated with each other.
Devise has a separate set of definitions in law, and the legal term does function as a noun referring to (1) property or lands given by will or (2) the act of transmitting such property or lands. But this information is mostly useless to nonlawyers, for whom devise is for all intents and purposes only a verb.
Devise is often mistakenly used in place of device—for example:
Apparently a patron noticed the devise in the back parking lot of the movie theater. [Cape Cod Today]
Soon these devises were popping up everywhere on sidewalks. [San Mateo Daily Journal]
And these are positive examples:
A South Korean lawyer who is an avid user of the iPhone is waging a privacy battle against Apple over the device’s tracking capabilities. [Sydney Morning Herald]
That leaves little time for Congress to devise and pass a plan to raise the debt ceiling. [NPR]
Today’s devices possess larger hard drives and can record high definition signals. [Globe and Mail]
However, she quickly devises a devious lie. [National Post]