This was discussed in past.
There is no d2jsp app, and they don't plan on making one.
However, if you're using d2jsp from your phone, you can turn on the jsp notifications on your phone and get a Notification whenever some1 posts in your topic, messages you, quotes you etc.
D2JSP has a bad name around the web and is known as forum with bad reputation and bad leadership.
There is nothing that can fix that, especially not app.
There were topics related to this already, check them up.