I am not using a distro with an RPM package manager but I am sure RPM supports feed like package indexing. It is one the basic features of package managers. However, the problem is we don't have - I suppose - a repository with up-to-date rpm packages for Gumstix. So there is no reason fedora people are not doing good with their package manager :)
The first thing I'd try is to change default packaging format to ipk within Poky so as to have opkg as your default package manager. Then you could try using `opkg update` but I feel like it would give lots of version dependency mismatch errors.
I am just throwing ideas keep that in mind :)