Pinging a Device Every Second

How much compute and network resources does it take for a NMS to: 1. ICMP ping a device every second 2. Record these results. 3. Report an alarm after so many seconds of missed pings. We are looking for a system to in near real-time monitor if an end customers router is up or down. SNMP I assume would be too resource intensive, so ICMP pings seem like the only logical solution. The question is once a second pings too polling on an NMS and a consumer grade router? Does it take much network bandwidth and CPU resources from both the NMS and CPE side? Lets say this is for a 1,000 customer ISP.