The key point to keep in mind is that Pipes sucks - it doesn't blow. :-)

You can't force its output into another web service. You can have another service suck from Pipes, which is why I suggested DabbleDB. Set up a DabbleDB (online database) and you will be able to use its import feature to import a feed from a Pipe. It is run periodically (twice a day, IIRC).

Other idea (getting a bit Rube Goldberg at this point):

Dapper (dapper.net) has an email feature whereby it will send you a notification email when a nominated RSS feed changes. Using this, you could build up a history of a feed. To do the storage part, try this: create a blog (using Blogger). Get the "mail2post" address (ie any content sent to that email address will automatically get posted to the blog). Monitor your target feed with Dapper. Have it send update emails to your GMail account. Use a forwarding rule in GMail to forward those Dapper emails onto your blog (where they get auto-posted). This blog is now a persistent store of the target feed, accessible via HTML or RSS for future processing.

No code, just a whole of intertwined web services.