] Using a phone with Bluetooth, you can create a phonebook
] contact and write a message, eg. 'Hello, you've been bluejacked',
] in the 'Name' field. Then you can search for other phones with
] Bluetooth and send that phonebook contact to them. On their
] phone, a message will popup saying "'Hello, you've been
] bluejacked' has just been received by Bluetooth" or something
] along those lines. For most 'victims' they will have no idea as to
] how the message appeared on their phone.

bluejackq.com: What is Bluejacking?