@ambientdroid - could you explain your suggestion with contact apps? Do you have other apps (such as WhatsApp, for example) that do integrate with contact apps? How?
Viber for PC/Mac is a future plan of ours, but no official dates yet. We acknowledge the demand among users, and working these days to plan it.
@John Huang - Viber is a VoIP app that lets you talk and text over the internet.