I doubt and don't think they should feel threatened. If I were them I wouldnt be guarding my application because it's a very simple and easy to replicate concept. The real value is in the service. You pay for StatusPage because you expect they'll have better uptime than you and they allow you to focus on building your app and communicating with your customers. They take the work of building and maintaining a status page away. Pingdom is very similar. Something you could definitely build yourself but why bother when you have better things to do with your time.