This feature is available in the current version of vBulletin, as well as the ability to view the last 10 visitors on any profile. I suspect we'll see it once Dani upgrades the site (which apparently takes a while due to its complexity).
It's possible that this will be implemented in a future version since it is a default feature of the most current incarnation of vBulletin. However, it's not something I plan on doing in the foreseeable future. We're most likely not going to upgrade to the latest vBulletin version until the end of 2009.