Now that Google has made us used to everything 'instant' (I don't even like instant coffee) we know anyone with a SOA algorithm and piece of hardware/software should be able to instantly predict. And I thought that 'nowcasting' was too shorter term! Not to mention that one shouldn't be confusing speed with accuracy; you can't have both. Remember!
As a final thought, if you need to predict half a second ahead, would it be too much waiting that time in order to get the real figure? Just kidding! Think of finances for instance.