I am a Pingdom customer and I think the thing that could make me shift is an enhanced form of custom check - like what Pingdom has today but better.

In my setup I made a public service where external tools can retrieve some realtime stats like current number of users, queue lengths, number of jobs processing etc. Pingdom uses this service in different custom checks and it kinda works, but I can't use the stats or graphs for anything. Not all checks should be described in a status code and response time - a simple number would be great. Make graphs with that and allow users to set a threshold for when alerts should be sent.

Another thing missing is support for basic authentication.

As others have noted your front page is not really getting the message through.