I've started working on a Historical Volatility (HV) indicator for NT7 both because I need it and also to test the futures.io (formerly BMT)Codex. Version 1.10 is posted there for development, and when it is ready for production use I'll post it in the downloads section.
The code posted works (as in it plots), but it is not 100% in line with the HV numbers I get from other sources.