This feature is now supported in 11.2 on SRX100, SRX210, SRX220, SRX240, and SRX650 platforms.
• IP Monitoring with route failover (for standalone devices and redundant Ethernet interfaces)—This feature is supported on SRX100, SRX210, SRX220, SRX240, and SRX650 Services Gateways. This feature monitors IP on standalone SRX devices or chassis cluster redundant Ethernet (reth) interface. Existing RPM probes are sent to an IP address to check for reachability. The user takes action based on the reachability result. Supported action currently is preferred static route injection to system route table.
There is a also script which can be used to simulate the track-ip functionality. It allows for path and next hop validation through the existing network infrastructure with the ICMP protocol. Upon detection of a failure, the script will execute a failover to the other node in an attempt to prevent downtime.