While under-development, we suggest you check out:
DoodleChat.com
Or for mobile apps try:
The most FUN doodle app we've found, Doodle Toy! it will let you post your messages to Facebook or send by MMS text message or Gmail/Email also!
DoodleToy.com
Or try the more advanced Doodle Texting app:
DoodleText.com
Soon we hope to bring you more Reviews of great Apps and online systems for Doodle Messaging.