Does not look good for 3GS owners until Apple gets around to releasing a patch:
The [SMS] vulnerability allows an attacker to run software code on the phone that is sent by SMS over a mobile operator's network. The malicious code could include commands to monitor the location of the phone using GPS, turn on the phone's microphone to eavesdrop on conversations, or make the phone join a distributed denial of service attack or a botnet, Miller said
