YMess in Yahoo Messenger Chat Client for Java Mobile Phone. YMess could be the stand for Yahoo Messenger, Y for Yahoo, Mess for Messenger. YMess Features are Contact List, Fast Data Transfer, Instant Message, Emoticons, and many more. To Install to your Cell Phone aka Mobile Phone you required : Java Mobile Phone, MIDP 2.0, CLDC 1.0 enable devices. YMess is Freeware software so be happy to download and run it freely.
For other YM Mobile Chat Client you can try YmTiny and Yamee.