No.1 D5 can install Viber as well Zalo on it.
if you 're wearing a No.1 D5 , you shoud install on it a very useful app, it is floating toucher.
How do the apps affect battery life?
not much, it help you to avoid using to much the home button
When a couple of us tried FT in the past we got these results… it would be good if the developers had sorted out the battery drain problem 
https://plus.google.com/+AndrewDavis-the-omnipotent/posts/Dz9SZNSVorB
I am using easy touch. I heard that is was less battery consumption.
you should try floating touch, it 's very good, not error occour,