WatchXP is an addon I wrote while leveling an alt with some friends. It draws a marker on your experience bar for each member in your party who also has WatchXP and isn't max-level, showing how far through their level they are.

Commands:

/wxp config -Show the configuration panel

/wxp ask <player> -Request a marker for a player not in your group (they still need WatchXP)

/wxp ask <FirstName> <LastName> -Request a marker for a RealID friend (they still need WatchXP)

/wxp ask <n> -Request a marker for the nth online RealID friend in your friends list (they still need WatchXP)

/wxp toggle -Toggles the displaying of this addon on and off

/wxp refresh -Force an experience update from all players

/wxp version -Print the currently installed version number