Interesting idea -- seems there is something in the &quot;ether,&quot; as a LinkedIn connection just started posted her new company here:<p><a href="http:&#x2F;&#x2F;www.mystilla.com" rel="nofollow">http:&#x2F;&#x2F;www.mystilla.com</a><p>They use BLE devices with motion sensors which attack the same use case.<p>I like your idea better because it uses the built-in hardware just for laptops.<p>Not sure about what @betafish posted tho.