The use of mobile handheld devices within the workplace is expanding rapidly. These devices are no longer viewed as coveted gadgets for early technology adopters, but have instead become indispensable tools that offer competitive business advantages for the mobile workforce. While these devices provide productivity benefits, they also pose new risks to an organization's security by the information they contain or can access remotely. Enabling adequate user authentication is the first line of defense against unauthorized use of an unattended, lost, or stolen handheld device. This report describes an innovative type of authentication mechanism that relies on the presence of a signal from a wireless beacon for access to be granted. Such proximity beacons can be either organizational or personal oriented, and require only that handheld devices support a common standard wireless interface for Personal Area Network (PAN) communications, such as Bluetooth. Details of the design and implementation for both personal and organizational proximity beacons are provided.