Our HTTP check looks at the body of the URL you give it, and will return things like HTTP code, duration for the request, time to connect and receive the first byte, as well as a plethora of SSL information if applicable. As for transactions, you can send content or headers with the request if that works for your case, but you can not tell it to click a button or a link, etc.
We also support KeyNote - which does quite a bit more via their awesome XML Data Pulse API.