Does SentryOne Monitor SQL Data File Group Usage?
SQL Sentry (part of the SentryOne family of products) does monitor SQL Server datafile group usage both from a performance/acitivity perspective, but also from a space usage perspective. See some screenshots below in how we represent this for volumes, datafiles individually or as a group for a given database.
You can see we track usage as well as performance (latency and throughput) of your data files. Were you looking for something more specific?