Is there a way to make a tag pulse on and off?
With an expression tag based on getSeconds(now(1000)) you should be able to get a pulse. You will have to do some math on the result to turn seconds into a 1 or 0 based on how long you want the pulse to last. For example:
getSeconds(now(1000)) > 29
will be true for 30 seconds, then false for 30 seconds.