How to generate external secure form for clients in Rails

Hello,

I have an application where businesses can create accounts and add information about their clients. I would like to be able to generate a form that they can put on their website so that clients can automatically enter their info into the business's account. I know I might be able to do something like:

   <% form_tag my_site_url_with_action do %>    ....put here the fields for client info

But I was wondering if there is a way to make it secure by ensure that it's coming from my client's website as opposed from some spam website or so. Also I was wondering whats the best way to make it AJAX (with minimal inclusion of Rails JS for AJAX)

Any ideas?

Thanks,

Tam