As a software developer and web enthusiast I have one or the other domain in my possession. But it has always bothered me that "this one great domain" is already taken. So I attached myself to a number of APIs and built an interface that not only allows me to manage my domains but also to monitor domains that are already taken. If I put such domains on the "watchlist", the status is queried at regular intervals. As soon as the domain changes to a relevant status (shortly before expiration, cancelled, available on the open market), I will be informed via push notification / SMS / e-mail.