We support a range of different check types for all of the common services that we support. At the most basic, we are checking to see if a service on a given port is listening for connections - this is referred to as a "port check" in the control panel. For many of the most used services, including HTTP, HTTPS, IMAP, POP, SMTP and DNS, we also support more advanced types of checks where we, for example, download a full page from the web server using a URL that you provide, or perform an IMAP login session with credentials you provide.
We also support arbitrary TCP/IP port checks on whatever ports you specify, as well as Ping checks. If you have a specific application you need monitored, or are looking for more thorough checking for one of the services that we currently support, please contact our support team to discuss the specifics - we are continually expanding the portfolio of checks that we perform and most likely can accommodate your request.