Pingdom is a suite of tools around site speed & uptime monitoring. You can run its standard tools on your own site, or on competitors, where it will ping any pages you choose at regular intervals. Off the back of that it can alert you of any downtime (either via email or text message), and provides dashboards and reports of changes in site speed, uptime, etc, from any of its data centres across the world. Alongside that they offer a ‘real user monitoring’ tool that measures site speed from the point of view of your website users (it gathers this information from browsers as users hit your pages). Google Analytics can do something roughly similar, but Pingdom’s advantages are they use ‘median’ values rather than ‘mean’ averages which are much, much, much more useful in this context, and they offer much neater tools to drill into this by browser, page, location, and to set thresholds to allow you to set and monitor site speed KPIs. The pricing is pretty good, with the caveat that it gets expensive as soon as you want to add multiple users, and that their multiple user access tools aren’t that great for agencies.