I have started building Kamailio RPMs for Fedora 20 & 21 and Enterprise Linux 7. Currently, the RPMs are based on the 4.1.4 release, with updates applied to keep it in line with upstream's development branch.
You can browse the spec file and patches here. Feel free to contact me if you see any issues with the packaging.
Right now, the RPMs are available in the mss-testing channel of the Fedora & Enterprise Linux RPM Repository, though I plan to move them out of mss-testing and into the default mss channel in the future.
I have also begun integrating Kamailio with Asterisk at Messinet Secure Services to enhance the capabilities of the communications services we provide. I'd love to hear from you if you have any pointers!