I think it would be best if any software like that were open source, and to be honest the masternode checker too, or is it already? I don't want to take anything away from your work, but I think the need to trust should be reduced when possible. What do you think about setting a target of Dash donations to publish the source code? I would be more than willing to contribute.
As for the alert app, as it is, it only reads publicly available data using an address you give it. Not a lot of point. Plus, everyone would then see how terrible my development skills are
So how can one be sure that the app doesn't call home with the IP address of the user making the masternode queries? I'm not suggesting that you are doing anything like that, but if you did want to target holders of large amounts of Dash an app like that would probably be a pretty good way of singling them out.