Heartbeat monitored by Pixracer from companion computer (RaspberryPI)

I have a setup where a Raspberry Pi is commanding the Pixracer. The PI handles everything including passing RC controls through a serial link. I have had issues with flyaways when the PI dies and the last known RC command continues to be executed, and my failsafes, implemented on the PI, do not take effect because of sudden power loss. Is there a way to have the Pixracer listen for a heart beat from my onboard PI so that if the PI dies, the Pixracer will execute a BRAKE?