Ask HN: Added value gateways for s3-like cloud storage providers?

As part of a server backup strategy I'm looking for a service that can sync Amazon S3 buckets to Rackspace cloud files (or any other storage provider).

The only service I've found so far that does this is SMEStorage (http://www.smestorage.com). To describe what they do is easier if I just lift the text from their home page:

"We spend our time thinking about the way we can add value to storage clouds. We created the SMEStorage platform to enable us to add such value! We take existing storage clouds and layer additional features and better ways to access files. Things like encryption..."

On the face of it it seems like a decent idea but I was surprised I couldn't find out much about them which makes me apprehensive.

Do you know of any other cloud gateways that offer similar functionality? Or have you used SMEStorage?