Textr enables similar threaded text messaging functionality as the Palm threaded solution that is found on the Treo 700w/wx and the 750. here are the features:
Organize conversations by the message sender
Store and archive SMS conversations on storage card
Integrate contact photos using the default contacts
Quickly view read, unread, and new text messages with icons
Access Textr and unread messages with a Today screen plugin
See messages with a pop-up that displays contact photos.
Head over to Textr to see screenshots and download a trial.