Unfortunately, IOS (Ipad,Iphone) and Android do not support Opentype. IOS are suppose to support AAT fonts, but you won't be able to embed AAT fonts for Arabic into your application without some kind of hack. This is a well known bug, and I'm not too sure if it has been fixed. Even if it is fixed, it is rare to get a good Arabic AAT font. The one and only that I know is from SIL (as mentioned, you still can't use it to embed it into your app).
I've created a workaround to embed a font into your IOS and Android App, but it it not a standard arabic font, so it is not easily used by anyone.