Here are some of my favourite tools for web perf and analytics:
Uptimerobot.com - Free tier. 50 monitors. Sends a request every 5 minutes to a website.
Pingdom.com - Free tier. Gives average response times.
Azure have an excellent uptime monitor inside Application Insights
Builtwith.com - eg is this a wordpress site, what webserver etc..
Deadlinkchecker.com This handles redirects well
Apache benchmarks load testing from the command line