3rd party network monitoring

In light of the recent major outages experienced by XO and Abovenet, I have become very interested in finding a 3rd party vendor to monitor the availability of my network from a variety of locations. I've looked at keynote / redalert, but oddly enough they don't seem to be able to monitor simple ICMP round-trip times - they (or at least the sales folk that I've spoken with) insist on checking the status of a TCP port or the response time of a web server. Google searches have yielded a few leads, but nothing terribly promising. Can anybody recommend a vendor for this type of service? I suppose I could always just get a bunch of VPS accounts here and there and run smokeping, but I'd really like to avoid that. - Darrell