A simple bash script that pingfloods an array of IPs/hostnames and outputs a JSON of the status of each item in the array, as well as the last date and time of the execution.

Heartbeat.sh

#!/bin/bash

SERVERS=( 192.168.12.5 192.168.12.10 192.168.12.15 192.168.19.1 192.168.20.1 )
STATUS=()
ArrayID=0
Entries=${#SERVERS[@]}
Counter=0
LastDate=`date +"%Y-%m-%d"`
LastTime=`date +"%H:%M"`

for i in "${SERVERS[@]}"; do
STATUS[$ArrayID]="OFFLINE"
((ArrayID++))
done

OUTPUT=$(for i in "${SERVERS[@]}"; do
# Non-root users can't pingflood. Adapt the interval / -f option
timeout 0.2 ping -c 2 -f -i 0.1 $i > /dev/null 2>&1
if [ $? -eq 0 ]; then
STATUS[$Counter]="ONLINE"
fi
echo "\"$i\":\"${STATUS[$Counter]}\""
((Counter++))
done)

TIMESTAMP=$(
echo "\"date\":\"$LastDate\""
echo "\"time\":\"$LastTime\""
)

echo -e "{$OUTPUT, $TIMESTAMP}" | sed ':a;N;$!ba;s/\n/, /g'