module SimpleForm

def self.wrappers(*args, &block)

and store it in the given name.
Define a new wrapper using SimpleForm::Wrappers::Builder 
def self.wrappers(*args, &block)
  if block_given?
    options                 = args.extract_options!
    name                    = args.first || :default
    @@wrappers[name.to_sym] = build(options, &block)
  else
    @@wrappers
  end
end