I'm specifically needing to know about NetTutor and GMetrix. Any guidance/assistance you can provide would be greatly appreciated.
A list of integration partners is available from the Integration Hub, https://integrationhub.brightspace.com/
This list is by no means exhaustive. Other external or 3rd party tools supporting the Learning Tools Interoperability (LTI) standard, not listed, can easily be integrated into your Brightspace environment.
GMetrix and NetTutor support LTI enabling you to integrate them into your environment. Documentation for each provider is listed below:
Depending on the version of LTI supported by the external tools Brightspace documentation is available from:
Hope that helps!