Well you need both a platform and feature set that supports OER or PfR. You'll generally find software routers with 12.4 (and a services image?) support OER; with 12.4T PfR (sort of OER v2). Some switches also support OER/PfR, but I believe with more limited features. Such as, I recall, no support for running as a master controller nor NBAR analysis.
You'll want to insure the OER/PfR features support what you intend to do. For instance, before the PfR PIRO feature, OER/PfR only supports BGP or static routes.
You'll also want to decide whether you'll run the master controller on a dedicated router.
To learn more, you might want to start here: http://www.cisco.com/en/US/products/ps8787/products_ios_protocol_option_home.html