Follow these instructions to set up one-click access to Yahoo! Messenger on your phone.
Register your mobile phone
Sign in to Yahoo! Messenger via text messaging:
Note: During registration, if you select the option for automatic sign in, you will ALWAYS be automatically signed into Yahoo! Messenger on your mobile when you log out of Yahoo! Messenger on your desktop.
Once you are logged into Messenger on your phone, your Yahoo! Messenger contacts will see you as "available" with a note that says "I'm mobile."
Some tips for using Yahoo! Messenger via text messaging:


Yahoo! Messenger via text messaging, or SMS, is currently available* in the following countries: Australia, Canada, India, Indonesia, Malaysia, Philippines, Thailand, United States, and Vietnam. Service in these countries can only be accessed from the desktop.
*Note: Availability within countries varies by carrier. Check with your wireless operator for details.