BuddyCheck

Tools that allow you to check the status of your friends can be found on various web pages. BuddyCheck is an application that allows you to check the invisibility status of other users that possess a Yahoo! Messenger account, on your very own computer desktop.
The application is easy to install and offers a friendly user interface that features elements found in other Instant Messaging apps.
The main window will display all the buddies you've added, so that you can keep a close watch on them.
Unlike web-based apps, BuddyCheck requires a valid Yahoo! account so that it can be used properly. Thus, before using it, you need to add your messenger credentials, connect to Yahoo! and then check the status of other people.
Note that multiple accounts can be added and contacts can be imported with the help of the Accounts menu.
Moving on to the checking part, you can notice that the people you want to verify can be added with the help of the Contacts menu. A location that also offers you the possibility to view the users that are offline or are disabled.
The program can also verify a user's status automatically. You can set the exact amount of time you want to check-up on an account from the Contact Details window.
Some customization options are also available. All you have to do is access the dedicated window. Once here you can select the server host and port you want to use.
Among other options you can choose to autoconnect on startup, start the application when the system boots, minimize the application to the system tray, activate the balloon sound for notifications or keep a presence log.
BuddyCheck is a simple and handy tool that can help you can act as a little spy and monitor the friends that are hidding from you.