There are many VPN (Virtual Private Network) applications for Android, but this is the only one that works with the Android System Settings, which is the most convenient way to access your network settings and connect to a VPN. It has a lot of options, like which protocol you want to use, which country you want to connect to, etc. It is also possible to add your own protocol and use it as a proxy for all your network requests.

VPN Settings is not an Android emulator, but it is a native application and it works as a standalone package.