Re: Website uptime monitoring
personally I wouldn't use them...
if a machine is under excessive load, a third party adding more load in the name of 'checking your connections speeds' isn't going to help matters. in my opinion for things like load checking and connection speed checking you are much better off doing this yourself, (aside from anyhting else you can also have hardware condition reports sent to yourself as well).
so far as your site sending the correct content (one of the listed features) how do they know what your site is meant to carry? will you get false alerts each time on dynamic sites, or if there is some kind of feedback...
there is only two ways that your site can display incorrect content,
1, the DNS has been altered to point at another server
2, the site has been altered by either a hack or a virus (like poison box)...
in both of these cases an email wont actually help you that much!