There was some efforts to do that with bluetooth such as http://www.mulliner.org/bluetooth/bluespamfaq.php but most folk are smart enough to turn that off.
I have no depth of knowledge related to the new NFC (near field communication) technology that is being used in smartphones, but my question has to do with its uses. Can NFC be used as a "hotspot" for phones as they walk by a certain location? If not, is there any technology out there that would allow phones to be in the premesis of a "hotspot" and receive notifications? (like push notifications on iphones)