Yahoo! status checker is a status indicator that detects invisible users on Yahoo! Messenger. With Yahoo! status detector you can find out their real online status. Yahoo! status checker shows your friend avatar and also gives you the possibility to download it. Yahoo! indicator status works for all versions of Yahoo! Messenger , web messenger or e-mail. Use now http://www.yahoostatus.org
i always use buddy-spy..
try google for it, nice software…
the tool used above are web-based. means no need installation