Naya, F., Noma, H., Ohmura, R., and Kogure, K. 2005. Bluetooth-based Indoor Proximity Sensing for Nursing Context Awareness. In Proceedings of the Ninth IEEE international Symposium on Wearable Computers (October 18 – 21, 2005). ISWC. IEEE Computer Society, Washington, DC, 212-213. DOI=

This is not a very good article for learning a lot about Bluetooth, however, for people familiar with Bluetooth it does talk about a few interesting ways of using Bluetooth for proximity detection, and how you can improve upon the simple method I am currently using.