In fact, this can be done but requires adb to be installed (Part of the android SDK)
adb shell am start -a android.intent.action.SENDTO -d sms:CCXXXXXXXXXX --es sms_body "SMS BODY GOES HERE" --ez exit_on_sent true
adb shell input keyevent 22
adb shell input keyevent 66
Where CCXXXXXXXXXX is country-code followed by phone number. This may not work correctly on non-standard android installations, you will need to find the correct keyevent values to pass.