As you know, Yahoo! Messenger for the iPhone allows you to IM friends and family right from your iPhone wherever you are. This is a great app but something was missing: the ability to chat with your Windows Live Messenger contacts. I’m happy to announce that our colleagues on the Yahoo! Messenger team recently released a new version of the Yahoo! Messenger App for the iPhone (and iPod Touch), which allows interoperability. You can read more on their blog post
So now, on top of being able to IM your Yahoo! contacts on the go, you’ll now be able to chat with Windows Live Messenger contacts just like you do from the Yahoo! desktop client and within Yahoo! Mail.
You can download it directly from the Apple App Store.