Monitoring vShield using vCloud Networking and Security 5.1.x REST API

We've had vShield 5.1.2 become disconnected from our new vCenter 5.1.0 server more than once.  And, we need to know when that happens.  In the configuration screen, we see Last successful inventory update was on m/d/Y I:M:S p (Z).  But, I could not find this information in the API.  Does anyone know where I can grab this?  Or, should I just use the API to synchronize the vShield Manager with vCenter server every once in a while?  I strongly prefer monitoring it so that I can know exactly when it breaks and how often.

I don't think getting a vShield heartbeat (though cool) will help me to be sure that the vCenter connection checks out.

The vShield API Programming Guide has a some nice samples; but it's incomplete.  I'd love to have a reference document like vCloud has.

Thanks for any help!