Membership system is almost necessary for all mobile apps, on the other hand, users need to remember so many passwords for different services. So besides general registration form, adding Facebook Login function is very important for those who don’t want to remember another password (over 90% of users based on our experience).
Push notification services let you to push message to users any time you want. Unless users disable push notification to your app, normally they will see your push message, this is a very powerful marketing channel.
Geolocation service let you to get the current location of a user. You can provide customized services to users based on their locations, such as restaurants nearby, etc.