WhatsApp (Compatible with iPhone)
WhatsApp works by analysing your iPhone’s contacts and allowing you to chat to them, for free. Full video calling is not yet available on WhatsApp, but is coming very soon; and for the time being, you can send short videos to your friends and family. There are third-party applications which work in conjunction with WhatsApp, such as
Booyah. The application works with WhatsApp, in order to allow you to make video calls to your WhatsApp contacts. See more: How to group video chat on iPad or iPhone.
Its biggest limitation is that you need a phone number in order to make the app work, which is not entirely ideal for iPad and iPod touch users – but there are some workarounds in the article linked below. Unlike Viber, WhatsApp doesn’t have a solution for users who don’t have a physical SIM card in their devices.
However, you’ll be able to find third-party apps, such as Messenger+, which provide you with a means of using WhatsApp on iPad.
How to install WhatsApp on an iPad (without jailbreaking).