William Chu sent me a working configuration he uses to measure jitter with the IP SLA tool and react to excessive jitter on the primary link. First you have to create the jitter probe with the IP SLA commands:

ip sla monitor 3000
 type jitter →
   dest-ipaddr 199.11.18.168 dest-port 12333 →
   source-ipaddr 199.11.18.169 codec g729a →
   codec-numpackets 100
 tos 184
 frequency 10

Note: The continuation character (→) indicates that the configuration command spans multiple lines

Next you have to define the IP SLA reaction to excessive jitter. William configured his router to react when the jitter exceeds 300 milliseconds and returns back to normal when the jitter falls below 290 milliseconds (some hysteresis is always a good thing).

ip sla monitor reaction-configuration 3000 →
  react MOS threshold-value 300 290 →
  threshold-type consecutive →
  action-type trapOnly

As the last step in the SLA configuration, you have to start the probe:

ip sla monitor schedule 3000 →
  life forever start-time now

After the SLA probe and out-of-bounds reaction have been configured, the router will generate syslog messages whenever the jitter gets above the threshold as well as when it falls below the second threshold. You can then use the EEM applets to act on the syslog messages:

event manager applet MOS-Below
 event syslog occurs 1 period 120 →
   pattern "Threshold below for MOS"
 ... actions ...
!
event manager applet MOS-Above
 event syslog occurs 1 period 120 →
   pattern "Threshold exceeded for MOS"
 ... actions ...