Short Answer: yes.
Long Answer: Yes, but…a full answer to this question includes a technical answer and a practical concern.
First, the technical answer
You can install a .pkg or .mpkg using this syntax:
sudo installer -verboseR -pkg "/path/to/pkg/foo.mpkg"
If the installer isn't 'signed' properly, you'll need to add -allowUntrusted
sudo installer -allowUntrusted -verboseR -pkg "/path/to/pkg/foo.mpkg"
You may also need to specify where you want it installed, using -target / (I'm not 100% certain this is required, but it's a good idea):
sudo installer -allowUntrusted -verboseR -pkg "/path/to/pkg/foo.mpkg" -target /
Now, the problem is that sudo is going to ask you for your administrator password when you try to run installer. If you want to automate this, you need to tell your Mac not to require your sudo password when running the installer. To do that, you can add this line to your /etc/sudoers file:
%admin ALL=NOPASSWD: /usr/sbin/installer
See man visudo for instructions on editing that file.
Second, the practical concern
If you are the only person who uses your Mac, adding the above line to /etc/sudoers is not a big deal.
However, if this is a shared Mac, then other people who are in the 'admin' group will be able to run /usr/sbin/installer without being prompted for their password.
Also, obviously if someone gets into your 'admin' account, they too could, theoretically, cause mischief with /usr/sbin/installer. Although I am at a loss to think of exactly what they would do, it's a trade-off of security versus convenience.
Third, a github script
I wrote pkginstall.sh to do some nice things like log the process, as well as tell you whether or not you are supposed to reboot after installing the package.
Last but not least: Automate "how?"
As far as how you want to automate the installation, that depends on more specifics of what you are trying to do. You could, for example, make a folder such as ~/Action/AutoInstallPKG/ and tell launchd to install any .pkg or .mpkg files that are added to that folder, and then move it aside afterwards.
I have been meaning to do something like this for a long time, and so I finally put it together. You can find it at https://github.com/tjluoma/autopkginstall. Installation instructions are included at Github, so I won't repeat them here.
This is actually a macOS Gatekeeper issue try these steps:
To resolute Gatekeeper issues on macOS Sierra you might have to partially or completely disable Gatekeeper checks.
Option I
For a certain application run in Terminal:
sudo xattr -rd com.apple.quarantine /Applications/[LockedApp].app
Option II
To disable checks globally run in Terminal:
sudo spctl --master-disable
Best Answer
You're using a signing identity that can only be used for Mac App Store distribution. You cannot sign with that identity and test it on your own Mac before submitting it to the Mac App Store - it won't pass GateKeeper validation.
If you want to create an installer for distribution outside the Mac App Store, you'll need to use a signing identity prefixed "Developer ID Installer".