How to configure XBee to send command when signal is lost

I am using an XBee S6B to relay signals from a computer to a FPGA device to control a robot. I use Hyperterminal to send commands over WiFi to the XBee which is connected to the FPGA to control motors. I was wondering if there was a way to initiate a protocol that if the connection is lost, a signal (preferably 8bit code) is sent so the FPGA will kill the motors. Are there any ways to do this if I am just using one XBee or do i need to use two Xbee’s?

You can query the AI command but tht is about it.