I used the old version, a Behringer Feedback Destroyer and the M-Audio midi controller to tame a couple nasty bass peaks in my room. Haven't tried the new one yet.
I was just using a RS SPL meter for a mic.
I think REW is really only for "analysis". You can use a BFD or some other device on low frequencies, but calibration takes advanced algorithms and processing power like Audyssey. And even then, you have to wonder whether you're making things "better".
You can use REW, a mic and a compatible soundcard (I have the old Sound Blaster external one that is referenced sometimes on the site) to generate lovely charts, graphs, etc.
What you choose to do with the charts and graphs is kind of another matter.
