Mobiles as access control tokens

Mobile Access Control: Exploiting the BYOD Trend (IFSEC Global)

With today’s mobile access technologies, smart devices can be used as universal credentials for accessing multiple buildings, IT systems and other applications using NFC and bluetooth. These devices provide users with extremely convenient vehicles for opening doors and performing other tasks that require the presentation of a secure credential.

There's a lot of good information in the linked article and it's written by the director of Strategic Business Development and Innovation at HID, and you'd expect that they've been putting a lot of thought toward what access control is going to look like after prox cards.