CheddarGetter has had this feature for awhile.
http://www.braintreepayments.com/services/pci-compliance
edit: So, w/ Recurly I wonder if it's the same thing and I'd need to do the Self Assessment Questionnaire A when using recurly.js
We launched our own Transparent Post back in March 2011. We created Recurly.js to simplify performing client-side validation, pricing calculations (w/ coupons, VAT, add-ons), and proper error handling when a transaction is declined. It's 10x easier to implement than Transparent Post, and has a much better user experience for the customer.
But, going to hold off for now and just use hosted payment pages for a bit. Will likely use this in the near future though - thanks to the Recurly team.