As was mentioned, you could install a VNCserver on your rooted smartphone and it would allow you to do what you require. I know it sounds a little counter-intuitive at first, but to display the smartphone screen on the pi's monitor, the VNC server goes on the smartphone and the VNC client goes on the pi. In fact this is what I will be trying next, as soon as I root my new Nexus 4 phone, but I will be doing it wirelessly. There is even a non-rooted app version, but I have not read the limitations.
Yesterday I was able to get this to work in the reverse direction; display my pi's screen on my smartphone wirelessly. I used the Android FreebVNC app on my smartphone to accomplish this. What is really nice about the app is that it does SSH tunneling for you (no extra steps) and has a couple of other secure methods of communication as well. Granted, kind of ridiculous on a tiny smartphone screen, but I was able to start and run applications and such from the gui. Pretty cool. To be honest, I really just wanted command line access from my smartphone to my pi; for that I installed ConnectBot. It sets up a ssh connection from the smartphone to the pi and has some great features, like you can increase the size of the text to make it very readable.
My Raspberry Pi Project Page: