You may get emails' from Google saying that access was requested from random locations you have never been to before, this is because I'm not using the proper authentication system from the Google Play services, and am making the POST request manually. In the Casper app Usage Agreement, I explain that you can create a random Gmail account just for logging into Casper, it doesn't matter what account it is as long as it is a valid Google account so I can authenticate. I encrypt your email and password with the Google server's Public KEY and then send it to the server to get the data I need to send in Snapchat's login. I can't use these credentials as the built in Google Play services flow won't allow me to authenticate as the Snapchat app, (can't authenticate with the Snapchat package name) so I have to manually make these POST requests. The official Snapchat android app uses the built in Google Play services system which uses the Google account that you setup on the device when you bought your device. In order to do this, I have to manually make POST requests to the Google servers to request this data.

When logging into the latest version of the Snapchat API, it requires a valid Google Authentication token as well as an attestation result signed officially by Google servers. I request your Google account Email AND Password so I can request authorization tokens and attestation results from the Google servers. I am the developer of the Casper Android app.

My comment gives you some insight as to why you are getting the email about an unknown device accessing your account.

Sign up snapchat with gmail