Any way to assign custom incomming SMS ringtones to contacts?

[SaosinEngaged]

This is, probably the only feature I miss from having a Blackberry. I like being able to tell when my girlfriend texts me while I'm at work just from hearing the tone, because otherwise I wouldn't answer it until I get out. It's not really a huge deal, but is there some kind of program that allows for this out there? Or am I missing the option to do this somewhere?

Seems silly that you cannot customize incomming SMS tones per contact, but you can with ringtones. Seems like something that should be standard by now across all smartphones.