imp:Software defined Radio

I'm a bit confused as to your intent here

there are several open hardware/software SDR system projects available from ham radio resources, though none that I'm aware of that specifically target

Bluetooth has a number of off the shelf chipsets that will interface nicely with any embedded/microcontroller hardware, you can look at their specifications and the core Bluetooth specifications to find out exactly what the major functional blocks of your system will need to acomplish.

if you are talking about implementing Bluetooth using SDR for the baseband, you arent talking about anything particularly difficult..

downshift the 2.4 ghz segment to somplace comfortable to work like 10mhz (there are chips available that will handle both downshifting for recieve, and upshifting for transmit) bandpass that to reject signals outside the band, digitize at 80 mhz or so -- and feed that to your DSP for FHSS signal detection and decoding (which is where you go talk to the DSP gurus)

On recieve.. Bluetooth uses 79 discreet frequencies, so an FFT could probably pick out the signals well enough, though that is probably somehat of a brute force solution. Implementing 79 filters in the DSP may be a more elegant method to watch all the frequencies in realtime. DSP guys would know better than me on that one.

on transmit -- you are essentially putting out one of 79 frequencies, one at a time according to the FHSS hopping pattern.. simple enough with a DSP frequency synthesizer.

A little more information on what you are tying to accomplish would help me give you a better answer !!