+1 on that. But, that was a feature of using HTML+Javascript applications rather then binary applications. So patching applications can't exist for Android applications in the same way. Unless someone ports the WebOS runtime to Android.
The only thing I know of is that in the market, there is a port of the official ics messaging app. So technically its still third party but its the closest to stock you can get. I believe it offers SMS split.
O to whoever else was saying it, yea whenever I tried the option in custom roms for SMS split, I too got the crazy symbols. The only app that has properly split for me is gosms which is typically my everyday messaging app.