In (American) movies I have often heard people say
Are you OK?
Are you ready?
I doubt this is proper English. Or is it? Is it colloquial only? Is it only American "slang"?
In an informal way, it's okay. Also, I observe that such sentences are spoken hurriedly. Also, in speech (especially in movies), they don't bother that much of grammar.
I won't say that as proper English but then, since they are quite common in their tongue, the natives make these sentences acceptable!