Not an expert here, but for registered, I would think that you would monitor changes from major nameservers. Wouldn't return 100% of the domains, but probably ~90%.
Looks great, I built a similar too but shuttered it after a couple years. I was able to get a few good domains in 2008 but once pre-emptive bidding on expired domain services like snapnames came around, it was much less useful.
I recommend adding a feature to filter domains that contain numbers/hyphens.
Thanks! I'm definitely planning on adding some more filtering options while keeping it as simple as possible. I'm currently considering using some other lib for the table too, as the one I'm using only allows sorting by single columns.
This looks like a great start. I'm kinda addicted to services like this. I pay for one called JustDropped as it emails me about expiring domains based on patterns I'm interested in and I've managed to pick up several reasonably valuable domains on the drop so far.