Very good price for 100 domains!
It will be even better when we'll be able to notify clients by email for a specific domain only!
The step to choose the error codes to monitor could be simpler also, I have some other tools and I don't have to select all the errors codes manually. I'm just interested to be notified when the site is down, and to have the information about the error code in addition.
Anyway, I see a lot of potential and usefulness!