One feature I've seen with other monitoring services is recording the amount of time a website/service has been down for. This is pretty useful information. For instance, when a scout reports that a website is back up after 5 minutes, your report would look like this:
Outpost::Scouts::Http: 'web page' is reporting up after being down for 1 hour.
Of course, this feature requires that each scout's state would have to be persistent, which could be stored in a yaml file or something. The backup gem does something similar where it stores all its state information, model definitions, etc. in ~/Backup.
You could alse disable this feature with a duration report option or something:
report :up, :response_code => 200
report :duration, false
Let me know what you think about this potential feature. I can help with these features if you need me to, feel free to assign any of them to me and I'll submit a pull request when implemented.