The current Dexcom transmitter is not Bluetooth as far as I understand. The Dexdrip hacking project is all about converting the radio (2.4GHz?) output to Bluetooth which can then be received by a mobile phone.
Note that the Dexcom Share receiver which is out now in the USA will forward the data to a phone via Bluetooth. The next version, G5, is expected to transmit Bluetooth directly from the transmitter.
In the meantime this website makes interesting reading regarding the Dexdrip project:
http://circles-of-blue.winchcombe.o...exdrip-test-results-vs-dexcoms-505-algorithm/
I also saw another page with more comparing the Dexcom receiver graphs & Dexdrip, but I can't find it right now. There was an interesting graph for the 2 hours as a sensor is restarted. I'll keep looking..