Is it legal to contact people by Bluetooth without opt-in consent?
The Information Commissioner’s Office previously said that Bluetooth messages are subject to the Privacy and Electronic Communications Regulations 2003, however, in a press release dated October 2007, it determined that bluetooth is not covered within this guidance. However, according to the Direct Marketing Association customers that have bluetooth devices may not be aware that their devices are set to discoverable, therefore technically speaking they have not necessarily opted-in to receive information from you by Bluetooth. See http://www.mobile.dma.org.uk/_attachments/resources/1720_s4.pdf for more information.
An opt-in is best practice when contacting customers by electronic communications.