3rd party network monitoring

[Darrell Hyde <dhyde () hostmysite com>]

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