DansGuardian, Snort etc - check out the competition
I found this interesting solution based on OpenWRT. OpenWRT + ASUS WL500g + USB drive ($160 TOTAL) offers Snort, DansGuardian, SPI, WPA2 and more.
Router and SPI functionality is described to work w/o the drive - so if HD fails the router/SPI is still working(after a reboot).
It would be great if embeded pfsense worked like that.