 const byte ackVal = 0b11110000;
 
 #if ROLE == ROLE_SENDER
+#define HEARTBEAT_THRESH_MILLIS 1000
+
 uint8_t triggerButtonPin = 2;
 uint8_t resetButtonPin = 3;
 
 Switch triggerButton = Switch(triggerButtonPin);
 Switch resetButton = Switch(resetButtonPin);
+
+uint8_t heartbeatLEDPin = 13;
+
+unsigned long lastHeartbeat = 0;
+bool isCommHealthy = false;
 
 #else
 #define TRIGGER_SERVO_ANGLE 90

    }
    else {
        Serial.println("Unknown failure");
    }
}
#endif


    if (radio.write(&val, 1)) {
        if (!radio.available()) {
            Serial.println("Empty recv!");
            return 0;
        }
        else {
            radio.read(&recvByte, 1);
