Ubertooth is an open source 2.4 GHz wireless development platform suitable for passive bluetooth monitoring. Building this device ..3 GHz costs about a 100$! This includes all the cost of the hardware. Kismet already implements passive Basic Rate Bluetooth monitoring. It is not compatible with bluetooth Enhanced Data Rate (EDR) modulations. The author has launched aKickStarter project and needs your support. This will end on the. 28th of February 2011. You can even get yourselves a completely assembled copy of UberTooth One!
Source: https://thehackernews.com/2011/02/ubertooth-open-source-bluetooth-test.html