http://www.cnetx.com/
It is $15 and it works pretty well, customizable, and has touch-flow capability. I have it in a tab with my Treo pic dialer for more on-screen pics (it is the bottom row of pics). You can press and hold for certain functions, I think you can assign it to SMS (I have it set to dial).
EDIT: I just tried, and SMS is not one of the options to set 'tap' or 'press and hold' to, but they are working on a new version, if you email them with the suggestion, they may already be working on it, or take it into consideration!!!
It is still a great app though!