Bafio has updated his Wifi Chat App for the DS:

Improvements to the touch screen code. You can now select sensibility to the touch using the "rainbow" bar. The sensitivity is displayed in the status info (top screen). Also, "jumps" are ignored.
Fixed issue with more than 6 users Up to 80 messages in the log. You can also use left and right to scroll messages.

More info --> http://bafio.drunkencoders.com/