I saw recently that Econet Controls (maker of the Bulldog water valve) have a smart gate lock in pre-production. There's a video of their latest prototype in action over here:
This lock is WiFi (unlike their other products that tend to be z-wave). I had emailed them to inquire about the possibility of a zigbee or z-wave version, but it doesn't look likely from the reply (see below).
However, it may be possible to "tasmotize" it (my speculation).
I know it's pre-production, but hope they are working on the mounting...that did not look very solidly attached to the gate, lots of wiggling/movement. I'd want at least a couple bolts top and bottom, rather than the current setup w/what looks like one at either end.