While there isn't a specific OSPF event detector, you could likely accomplish what you want in a few ways. One could be to have a syslog policy that listens for a message saying that a peer entered EXSTART. That policy will configure a second policy to listen for the transition message from EXSTART to EXCHANGE (or DOWN I guess). If that policy runs, then you're done. If not, a third policy will run to alert you that there is a stuck peer.
