I'd simply create a custom OID and monitor it centrally, but as you're looking for an email solution, I'd run the one-liner below on my Check Point management host to query the last backup status from all gateways and send the result via email once a week.
echo;chk=$(base64 -w0 <<<'NOW=$(date +%s); F=/var/log/CPbackup/backups/.last_backup_status; if [ -e "$F" ]; then BCKP=$(tr -d "." < "$F"); if [ $((NOW - $(date -r "$F" +%s 2>/dev/null))) -gt 2592000 ]; then BCKP="Last backup too old"; elif ! grep -q ucce "$F"; then BCKP="Failure creating backups"; fi; else BCKP="No Backups configured"; fi; printf "%s\n" "$BCKP"'); for gw in $(mgmt_cli -r true -f json show gateways-and-servers details-level full limit 500 | jq -c '.objects[]|{t:.type,a:."ipv4-address"}' | grep -v CpmiGatewayCluster | grep -v CpmiVsClusterNetobj | grep -v CpmiVsxClusterNetobj | grep -v checkpoint-host | jq -r '.a|select(.!=null)'); do printf '%-16s: ' "$gw"; cprid_util -verbose -server "$gw" rexec -rcmd /bin/sh -c "echo $chk|base64 -d|/bin/sh"; done