It seems to me that the only thing you monitor is the domain name, like pingdom. If this is the case, maybe you should make it clearer.
If not, you should make that clearer too. When I think of site monitor, what I want is to be able to monitor my hdd, cpu usage, ram spikes, main domains, etc. E.g. similar to serverdensity.com's offering.
Add some more info about exactly what you offer, and the cost. I know it says free on the sign-up page, but you should make it clear on the main page that this is a beta period.
Good job on actually launching though. Many people don't even make it that far!