[SR-Users] MWI handling

Hello. Trying to understand how to work with the presence_mwi module. It seems to me, that it's just for my purpose - inform subscribed peers about waiting messages. But it do not export any functions, noting. The scheme is simple: Peer->Kamailio->Asterisk. Asterisk can accept voicemail and when the message is saved I want to receive NOTIFY for subscribed peer. As I understand, peer should register on Kamailio, kamailio should accept this subscription and send subscription to asterisk. After this, need to proxy all NOTIFY to the peer. Anyway, cannot find any way to do that. How it's usually done, please, advice. Thanks in advance.