The following has been tested on ubuntu precise.

Install anyremote:

sudo apt-get install anyremote

Download the android client from here and install it on your android device (you may need to enable unknown sources in the settings).

Now run this on your PC:

anyremote -f /usr/share/anyremote/cfg-data/Server-mode/smplayer.cfg -s socket:5197

And now run on your android device anyRemote. Press the menu button and select Search. Select TCP/IP. Select the connection with the IP of your PC. That’s it, now you’ll see a screen with some controls.

There’s a gui interface, ganyremote, but either I don’t know how to configure or it just doesn’t work.

More info: http://anyremote.sourceforge.net

Edit: in order to use ganyremote in ubuntu precise is necessary to update it:

sudo add-apt-repository ppa:anyremote/ppa
sudo apt-get update
sudo apt-get install ganyremote