This thing has been out for years, since aim 4.0 when they allowed you to add mobile numbers to your buddy list. I've been using it for a while, but my friends get pissed at me.
If you IM a mobile device, they will receive the message with "Sent by SN message part # of #"
My friends have reported that they never get the messages in order, sometimes part 5 comes first then part 1 then 2, etc.
It wastes a lot of text and it doesn't come at once and they are all individual messages.
But hey its free on your part.