In Android, ensuring only pre-decided users can only use the app

Question

I'm making an app, which I will distribute via playstore. However, though the app can be installed by anyone in the world, it can only run for selected users who I know.

Below are the possible ways I have figured out,

1. Check the account E-Mail ids on the phone and if that matches with the one's saved within the app code.

2. Check the mobile number on the phone and see if that matches with the one's saved within the app code.

3. When the app runs for the first time, it will send an SMS to my phone. I will reply to that SMS either saying YES or NO. If I reply YES then only the app will run for that user, else it will not.

I would like your feedback on these mechanisms. If there are other ways let me know about that too.

Thanks...

Answer 1

I think your best options are:

1. Make users log-in using an e-mail and a password (you could ask the user to register and if he uses an e-mail that is known to you, send a password to that e-mail [make the user change it later though])
2. Beta testing - This allow you to choose wich users will be able to install your app by creating a community on Google+ to beta test your app.

Maybe both.