This is really a need for monitoring consistency of UX of any website.

Although I just think you should simplify your pricing model. I don't understand why you are talking about "requests". Who cares about bandwidth today anyway? Just make people pay for the number of pages the frequency of the checks.

Also, you should allow people to set up e-mail alerts when some parts of their website pages change (e.g. payment forms).

I would definitely pay for such product. : )