The MI (management interface) and Statistics APIs from Kamailio (OpenSER) were moved as libraries in sip-router.org.
In the future, the MI will be merged with RPC interface from SIP Express Router (SER) and statistics API will be improved to eliminate single lock system and provide more and better feedback from inside the SIP server.
Anyhow, for the first release of SIP Router, these APIs will probably stay as they are, to offer the backward compatibility with Kamailio (OpenSER).