Passing parameters to a script

Try this one:

import org.eclipse.xtext.xbase.lib.Functions

val org.eclipse.xtext.xbase.lib.Functions$Function2<String, String, Boolean> sendsms = [
	sms_text,
	sms_recipient |	
		logInfo ("script", "The sendsms script is called")
		logInfo ("script", "First parameter =" + sms_text)	
		logInfo ("script", "Second parameter =" + sms_recipient)	
		true
	]

rule "test"
when
	Item TEST_Trigger changed from OFF to ON
then
	logInfo("test","Test rule triggered")
	sendsms.apply("some text", "some recipient")
end

Since your return value is a Boolean you have to specify this in your Lambda.