MacID for iOS can be updated via the App Store like any other app, but because MacID doesn't connect to the Internet without your consent there is no way to push MacID for macOS updates to you automatically.
Thankfully MacID has implemented a clever way of letting you know there's an update. If you're running an older version of MacID for macOS, MacID for iOS will let you know under the device name in Connected Devices and send you a local notification.
Updating MacID for macOS
If you don't mind MacID connecting to the internet, choose "Check for update" under the Updates submenu. You can also choose to check for updates automatically and also install updates automatically in the future.
If you'd prefer MacID still didn't connect to the internet at all, simply continue allowing Safari Push Notifications for macid.co, and you'll receive a push notification to download from the website when a new version is available.
The latest version of MacID for macOS can always be grabbed at macid.co/get, and you can manually check for updates by clicking "Check for update" in the MacID menu.
Clicking "Check for update" will open a page on the MacID website which will check your version against the latest published version, and if you need to update you can download the latest MacID for macOS from there.
Since MacID v1.1 you don't need to delete the old version or drag MacID to the Applications folder; just double click on MacID in your Downloads folder and MacID can move itself.
If you allow this website to send you push notifications you can also receive notifications whenever a new update is available. You will not be spammed, don't worry!
You can also follow MacID on Twitter to keep up to date with everything MacID, and if you allow this website to send you Safari push notifications you'll receive notifications when new updates are available.