Ask HN: How would you deploy a Rails app onsite for a customer?

One of my new projects is a web-app for business (built on Rails). I've been fortunate to make some really good contacts who agreed to be beta testers (large corporate/franchise types).

One bit of feedback I received was that some companies may want their own instance of the app deployed behind a firewall.

Does anyone have any good ideas on how to implement this efficiently? Is there an easy to configure appliance that can run a linux distro and Rails stack? Is there any easy way it could pull updates?