This is one technology creativity that i admired so much, because With the newly produced and released of the Yahoo! Messenger for iPhone, all Iphone users now have the opportunity to make voice calls and video calling and connect with your IM friends in an exciting new ways.
Here are some features that this Brand newly released Yahoo! messenger for iphone came with.

FEATURES OF THE YAHOO! MESSENGERFOR iPHONE.

1. Video calls:
Now, iphone users are now afford the golden opportunity to Use the Yahoo! Messenger for iphones to make video calls, recieve video calls and stream live video one-to-one†.

2. Voice calls:
Now, as an iphone users, you are given the opportunity to make free voice calls to your Yahoo! Messenger friends.†

3. Low cost voice calls:
Now, as an Iphone user, you can now talk to your friends on their land line or mobile phone, and make low cost international calls for low costs with the newly released Yahoo! Messenger for iphones.
That's virtually known as cheap cell phones plan

4. Free SMS
With the iphone for yahoo! Messenger, you can now send and share short messages SMS, to your friends for free with your IM friends.

6. Connect and share goodies with your friends On pc.
With this newly released Yahoo! Messenger for iphone, you can now chat, send and recieve video calls, sms From iPhone to desktop and lots more.
you can now connect with your IM friends in any way you want, either through mobile application to PC, or vice-versa, that is through pc or your computer application to mobile application.

7. Free Instant Notifications:
now, you don't need to chat your inbox always to know when you've recieve a new message, the Iphone Yahoo! Messenger lets you know when a new message arrives, whether the app is running, or is in the background, or even if it’s not open, you can still get the instant alert.

8. Show and tell:
You can now capture and share iPhone photos and video in real-time, with your Yahoo! Messenger friends.

9. Multi-Task:
You can now run your Multi-task with other iPhone applications while Yahoo! Messenger is running in the background.

10. Medium for Fun
With the Yahoo! messenger for iphone, you can chat with all your friends in one place, whic means that you can now add your Windows® Live Messenger contacts to your buddy list.

11. Available and compatible Devices, informations.

Available for iPhone 3GS/4 users running iOS 4.1
Available to premium users in select countries.
Carrier charges may apply, that is your network provider may charge you.
So it's advisable to subscribe to data bundles plan and have a cheap cell phone plan.

PLEASE NOTE THAT:
This Yahoo! Messenger for iPhone runs on all iPhones.
Although, there are select features for some models, here are some features as listed below.

1. Video calling:
For the optimal experience, an iPhone 3 GS or the iPhone 4.0, iOS 4.1 & WiFi are also recommended too.

2. Voice calls to land line or mobile phone: Must be a Yahoo! Voice Phone Out subscriber in these select countries.
US,
France,
Germany,
Spain,
Singapore.

3. Multi tasking.
This is Available on iPhone 3GS or iPhone 4.0, iOS 4.

HOW TO DOWNLOAD YAHOO! MESSENGER FOR IPHONE

Step 1.
Visit this link with your iphone mobile.yahoo.com/messenger/iphone

Step 2.
When the link has opened, you should enter your phone number and download the app from the link that will be sent into directly your mobile phone.