The Messages Beta will Send iMessage to iPhones (Messages replaces iChat)
iChat can SMS to phones
It needs the computer to be listed as if it in the United States and contacting a Phone that is on a Carrier in the United States that is accepting SMS forwarding from AIM
You list the Buddy as AIM and then +plus their number as in +123456789
The computer can be made to "think" it is in the United States in System Preferences > International (or Text a Language in Lion) then Formats tab.
The Phone has to be a US phone with all the trimmings about AIM's SMS forwarding.
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Lion 10.7.3)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images." No, Seriously