Dynamic input form view, based on model? Is there a helper or plugin for this?

Hi,

Is there an existing helper or plugin that let's one define a dynamic
input form page based on a model?

For example I am going to have a tableless model to collect the input
parameters required for a report to be run. Given I have the model
(albeit based on a "ActiveRecord::Base Without Table"), is there a
helper or plugin that would let me say "render an input form for this
model, using validations defined in model"?

thanks