Currently we use NetBackup which does a splendid job of tracking tapes that have been sent off-site.
The question about whether such a feature would be available in v7 [for tracking/inventory of tapes that have been ejected after a backup job/sent offsite] was asked during the recent Backup to Tape Webinar, and the host of the webinar said that was a great suggestion and to request the feature in the forum.
It doesn't look like the attendee ever posted in this forum, so I thought I would.
I think this is a necessary feature as this is main reason tape it still used today, for off-site archival.
Can we expect to see this feature in v7? If we setup a job to backup to tape, then eject the tape once the job is complete, can we then automatically have said ejected tapes added to a "media pool" called "Offsite." This will help us track our off-site tapes and easily audit against the inventory list of say, Iron Mountain.