I forget where I found it but I have it set up so whenever I signout of yahoo instant messenger (YIM) on my phone, I get the IM's as a text and can reply to them just like a text and they go to the other persons IM. When I sign into YIM on a computer it automatically signs me out of YIM on my phone. no extra software needed.
Edit: I think this is it.
http://www.ymessengerblog.com/blog/2...hoo-messenger/