(OS X specific) I wanted to use a mobile phone style bluetooth headset as an audio input device for use in MAX but their native frequency is 8000Hz, which leads to audio issues when routed directly into MAX.

The answer is to set up a aggregate audio device in the macs “Audio MIDI setup” utility as this screen shot illustrates. (The important part is to choose the Built-In Microphone (or some other 44100Hz source) as the Clock Source. Then when you choose the aggregate device in MAX’s DSP status (now “audio status” in MAX 6) the input from the headset will be converted to 44100Hz automatically.

(also it does not hurt to check to make sure that “resample this device” is ticked when you right click on the headsets name where it is nested under the aggregate device title on the left.)