Ok. I just lost my nice write up on this one. Here goes another try.
Bryan,
fsutil.exe from microsoft can be used to provide details from NTFS and I'm sure that it will display free space.
SFW has alters that can be set to send notifications based on % free space on configured volumes. There are two alters (warning and critical) can be set with each sending notifications at a different % free space. SFW can also be configured to automatically grow the volume if needed although a patch may be needed to get this to work on some versions of the product.
Thanks,
Wally