Whoops, just saw this. :confused: Unfortunately, I didn't develop the app and couldn't tell you how it was done, and I haven't seen the developer who did make it (Martin Aronsen) in ages. :( Sorry!
That was a custom add-on provided by Martin Aronsen and is probably not available for redistribution, unfortunately. You could ask him (he's a member here), but I haven't seen him around lately.
On here, I think 20-something was the most I've received between sessions...however, on my site, we have an alert plugin that sends alerts every time someone mentions an artist you follow (even if they mention 20 artists in one post--you get 20 alerts :P), so I've gone into the hundreds there a...