Xbee S1 link status indication

I am using the S1 in AT mode as a serial pass through between two Arduino modules.

I would like to have a confirmed indication that the RF link is healthy … by a LED which remains ON for healthy link and OFF for a broken link.

I have read that the RSSI is not a confirmed indication as it can be activated by interfering RF signals also …

So what other options exist to implement this ?