Google's ad ambitions may reach further than you think. In a newly revealed letter to the SEC, the company said it could someday be serving ads on "refrigerators, car dashboards, thermostats, glasses, and watches, to name just a few possibilities," as part of a larger point about breaking out mobile ad revenue. As the definition of "mobile" expands, the company argued, it could encompass nearly any device that isn't a conventional computer.

The idea is particularly relevant after Google acquired Nest for $3.2 billion earlier this year, along with its next-generation thermostat and smoke detector. Together with Google Glass and the company's newly formed automotive partnerships, Google has already made inroads into most of the categories mentioned. Of course, none of those platforms are serving ads yet, but the letter suggests that advertising is still very much a part of Google's longterm plans.

Update: In a statement to Venturebeat, Google denied that the statement applied to its Nest acquisition, saying: "Nest, which we acquired after this filing was made, does not have an ads-based model and has never had any such plans."