No…Aqara and other companies sell homekit enabled buttons that you could just use outside, and they even advertise them for this purpose.
Happily I went to the Aqara website, and even ignoring that they seem to require a hub there this:
So no, they don't have a simple button that can trigger a HK notification.There are currently several products that support push notifications in Aqara products. They are: Door and Window Sensor, Motion Sensor, Vibration Sensor, and Water Leak Sensor.