I use paper.ly to scan my followers tweets for links relating to science education etc. It collates the resulting data into a newssheet, which is published on the web daily. I don't see that there is a data protection issue, because I don't have non disclosure agreements in place with any of them, This app is functionally similar, except the only person it notifies is the person who is subscribed to the twitter stream anyway.
Lets not be too politically correct here. Drawing an analogy with a phone call. Suppose a friend calls me and sounds down. I might do something about it. All this is is an automated system for drawing my attention to the fact that my friend sounds down and might need a little more attention than usual.
End of story.