Strings are untyped

Integers are untyped too.

Another idea was to store the type information in the name of the variable, like in the Hungarian notation. http://www.joelonsoftware.com/articles/Wrong.html

Strings are strings.

What you described, sounds a lot like good ol' typedef.

It solves one problem while introducing a bigger problem which is - everyone now needs to understand your 'new' type system.

Why not use named arguments instead of adding type annotations?