I’ve been desperately seeking a replacement for the old Dashboard Widget called Site Watch that would check any URL you want whenever Dashboard is pulled up. I just wanted something simple like that — something that runs in the background and gives me a heads-up when any of my sites can’t be reached. I’m surprised at how few apps there are for this, but of the few I found, this one is by far the best: Simple WebMonitor hangs out in the Menu Bar, pinging (in the background) any websites you choose as often as you like (every 2-60 minutes), and alerts you if there's any downtime. Totally intuitive, highly configurable, links to its own logs for details, can be launched automatically at login and silenced for meetings — it's EXACTLY what I wanted for keeping an eye on my sites' uptime. The perfect low-profile site-status monitor.