With this, I can realistically use my apple watch as a _standalone_ device to do pretty much everything I need.
This means I can switch off my iphone, keep use my apple watch as a kind of remote to my laptop. I can chat with my friends (not possible right now with whatsapp!), do some shopping, write some code, even read books!
This is just not possible now using an apple watch.
btw, WhatsApp has an Apple Watch App! https://faq.whatsapp.com/864470801642897