Gate Beam where to get a simple zigbee signaller

Hi there,
I’m hoping to build a gate/driveway sensor that tells me when people pass in through the gate on my driveway.

I have found PIR to be unreliable so I’m lookin at infrared beams instead.
Found this thing:

But as expected, it doesn’t have any zigbee capability.
I’d be hoping to add a battery and some method of zigbee notification to it.

So I’d be grateful if anybody could suggest a starting point with the zigbee part. Is there a transmitter out there that will just send a message when a circuit is closed? Rather than having to cannibalise a wall switch or something like that?