Man, when I saw that title, Electronic Equipment Tracking, I was thinking of something totally different, and completely awesome. But, oh well, this is kinda cool too.
What I want, and the requisite functionality already exists, is being able to page PDAs. They have noise functionality (i.e. the beep during scans), and they have serial numbers and IP addresses. Ergo, it wouldn't be hard to set something up on workbench or that desktop app (I forget the name; the one where you put the PDA in the cradle and can rebuild/update), where a lost PDA could be paged. Obviously it wouldn't work if the battery is dead or has been pulled, but it would go a long way toward recovering PDAs that some as***le workcenters are always hiding and would be a far sight better than walking every square foot of 150k sq.ft. store to check every shelf, waco, table, cabinet, etc.
These two things together would be even more awesome (sign-in tracking, plus paging).